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X-CSE-ConnectionGUID: iOJq6bsRQ1mqH9tuVt5glg== X-CSE-MsgGUID: LPwUKpSPQH2BBbzYZrxZbg== X-IronPort-AV: E=McAfee;i="6800,10657,11533"; a="68970249" X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="68970249" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:25:52 -0700 X-CSE-ConnectionGUID: mFiywEvyTiCAxUVk2a9p/Q== X-CSE-MsgGUID: DHS3og96Q0yCJmHB4RsCnA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="169779868" Received: from bergbenj-mobl1.ger.corp.intel.com (HELO wieczorr-mobl1.intel.com) ([10.245.245.6]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:25:30 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 01/19] kasan: sw_tags: Use arithmetic shift for shadow computation Date: Mon, 25 Aug 2025 22:24:26 +0200 Message-ID: <7e314394fc5643def4cd4c6f34ebe09c85c43852.1756151769.git.maciej.wieczor-retman@intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Samuel Holland Currently, kasan_mem_to_shadow() uses a logical right shift, which turns canonical kernel addresses into non-canonical addresses by clearing the high KASAN_SHADOW_SCALE_SHIFT bits. The value of KASAN_SHADOW_OFFSET is then chosen so that the addition results in a canonical address for the shadow memory. For KASAN_GENERIC, this shift/add combination is ABI with the compiler, because KASAN_SHADOW_OFFSET is used in compiler-generated inline tag checks[1], which must only attempt to dereference canonical addresses. However, for KASAN_SW_TAGS we have some freedom to change the algorithm without breaking the ABI. Because TBI is enabled for kernel addresses, the top bits of shadow memory addresses computed during tag checks are irrelevant, and so likewise are the top bits of KASAN_SHADOW_OFFSET. This is demonstrated by the fact that LLVM uses a logical right shift in the tag check fast path[2] but a sbfx (signed bitfield extract) instruction in the slow path[3] without causing any issues. Using an arithmetic shift in kasan_mem_to_shadow() provides a number of benefits: 1) The memory layout doesn't change but is easier to understand. KASAN_SHADOW_OFFSET becomes a canonical memory address, and the shifted pointer becomes a negative offset, so KASAN_SHADOW_OFFSET =3D=3D KASAN_SHADOW_END regardless of the shift amount or the size of the virtual address space. 2) KASAN_SHADOW_OFFSET becomes a simpler constant, requiring only one instruction to load instead of two. Since it must be loaded in each function with a tag check, this decreases kernel text size by 0.5%. 3) This shift and the sign extension from kasan_reset_tag() can be combined into a single sbfx instruction. When this same algorithm change is applied to the compiler, it removes an instruction from each inline tag check, further reducing kernel text size by an additional 4.6%. These benefits extend to other architectures as well. On RISC-V, where the baseline ISA does not shifted addition or have an equivalent to the sbfx instruction, loading KASAN_SHADOW_OFFSET is reduced from 3 to 2 instructions, and kasan_mem_to_shadow(kasan_reset_tag(addr)) similarly combines two consecutive right shifts. Link: https://github.com/llvm/llvm-project/blob/llvmorg-20-init/llvm/lib/Tr= ansforms/Instrumentation/AddressSanitizer.cpp#L1316 [1] Link: https://github.com/llvm/llvm-project/blob/llvmorg-20-init/llvm/lib/Tr= ansforms/Instrumentation/HWAddressSanitizer.cpp#L895 [2] Link: https://github.com/llvm/llvm-project/blob/llvmorg-20-init/llvm/lib/Ta= rget/AArch64/AArch64AsmPrinter.cpp#L669 [3] Signed-off-by: Samuel Holland Signed-off-by: Maciej Wieczor-Retman Acked-by: Catalin Marinas --- Changelog v5: (Maciej) - (u64) -> (unsigned long) in report.c Changelog v4: (Maciej) - Revert x86 to signed mem_to_shadow mapping. - Remove last two paragraphs since they were just poorer duplication of the comments in kasan_non_canonical_hook(). Changelog v3: (Maciej) - Fix scripts/gdb/linux/kasan.py so the new signed mem_to_shadow() is reflected there. - Fix Documentation/arch/arm64/kasan-offsets.sh to take new offsets into account. - Made changes to the kasan_non_canonical_hook() according to upstream discussion. Settled on overflow on both ranges and separate checks for x86 and arm. Changelog v2: (Maciej) - Correct address range that's checked in kasan_non_canonical_hook(). Adjust the comment inside. - Remove part of comment from arch/arm64/include/asm/memory.h. - Append patch message paragraph about the overflow in kasan_non_canonical_hook(). Documentation/arch/arm64/kasan-offsets.sh | 8 +++-- arch/arm64/Kconfig | 10 +++---- arch/arm64/include/asm/memory.h | 14 ++++++++- arch/arm64/mm/kasan_init.c | 7 +++-- include/linux/kasan.h | 10 +++++-- mm/kasan/report.c | 36 ++++++++++++++++++++--- scripts/gdb/linux/kasan.py | 3 ++ scripts/gdb/linux/mm.py | 5 ++-- 8 files changed, 75 insertions(+), 18 deletions(-) mode change 100644 =3D> 100755 Documentation/arch/arm64/kasan-offsets.sh diff --git a/Documentation/arch/arm64/kasan-offsets.sh b/Documentation/arch= /arm64/kasan-offsets.sh old mode 100644 new mode 100755 index 2dc5f9e18039..ce777c7c7804 --- a/Documentation/arch/arm64/kasan-offsets.sh +++ b/Documentation/arch/arm64/kasan-offsets.sh @@ -5,8 +5,12 @@ =20 print_kasan_offset () { printf "%02d\t" $1 - printf "0x%08x00000000\n" $(( (0xffffffff & (-1 << ($1 - 1 - 32))) \ - - (1 << (64 - 32 - $2)) )) + if [[ $2 -ne 4 ]] then + printf "0x%08x00000000\n" $(( (0xffffffff & (-1 << ($1 - 1 - 32))) \ + - (1 << (64 - 32 - $2)) )) + else + printf "0x%08x00000000\n" $(( (0xffffffff & (-1 << ($1 - 1 - 32))) )) + fi } =20 echo KASAN_SHADOW_SCALE_SHIFT =3D 3 diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index e9bbfacc35a6..82cbfc7d1233 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -431,11 +431,11 @@ config KASAN_SHADOW_OFFSET default 0xdffffe0000000000 if ARM64_VA_BITS_42 && !KASAN_SW_TAGS default 0xdfffffc000000000 if ARM64_VA_BITS_39 && !KASAN_SW_TAGS default 0xdffffff800000000 if ARM64_VA_BITS_36 && !KASAN_SW_TAGS - default 0xefff800000000000 if (ARM64_VA_BITS_48 || (ARM64_VA_BITS_52 && != ARM64_16K_PAGES)) && KASAN_SW_TAGS - default 0xefffc00000000000 if (ARM64_VA_BITS_47 || ARM64_VA_BITS_52) && A= RM64_16K_PAGES && KASAN_SW_TAGS - default 0xeffffe0000000000 if ARM64_VA_BITS_42 && KASAN_SW_TAGS - default 0xefffffc000000000 if ARM64_VA_BITS_39 && KASAN_SW_TAGS - default 0xeffffff800000000 if ARM64_VA_BITS_36 && KASAN_SW_TAGS + default 0xffff800000000000 if (ARM64_VA_BITS_48 || (ARM64_VA_BITS_52 && != ARM64_16K_PAGES)) && KASAN_SW_TAGS + default 0xffffc00000000000 if (ARM64_VA_BITS_47 || ARM64_VA_BITS_52) && A= RM64_16K_PAGES && KASAN_SW_TAGS + default 0xfffffe0000000000 if ARM64_VA_BITS_42 && KASAN_SW_TAGS + default 0xffffffc000000000 if ARM64_VA_BITS_39 && KASAN_SW_TAGS + default 0xfffffff800000000 if ARM64_VA_BITS_36 && KASAN_SW_TAGS default 0xffffffffffffffff =20 config UNWIND_TABLES diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memor= y.h index 5213248e081b..277d56ceeb01 100644 --- a/arch/arm64/include/asm/memory.h +++ b/arch/arm64/include/asm/memory.h @@ -89,7 +89,15 @@ * * KASAN_SHADOW_END is defined first as the shadow address that correspond= s to * the upper bound of possible virtual kernel memory addresses UL(1) << 64 - * according to the mapping formula. + * according to the mapping formula. For Generic KASAN, the address in the + * mapping formula is treated as unsigned (part of the compiler's ABI), so= the + * end of the shadow memory region is at a large positive offset from + * KASAN_SHADOW_OFFSET. For Software Tag-Based KASAN, the address in the + * formula is treated as signed. Since all kernel addresses are negative, = they + * map to shadow memory below KASAN_SHADOW_OFFSET, making KASAN_SHADOW_OFF= SET + * itself the end of the shadow memory region. (User pointers are positive= and + * would map to shadow memory above KASAN_SHADOW_OFFSET, but shadow memory= is + * not allocated for them.) * * KASAN_SHADOW_START is defined second based on KASAN_SHADOW_END. The sha= dow * memory start must map to the lowest possible kernel virtual memory addr= ess @@ -100,7 +108,11 @@ */ #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS) #define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL) +#ifdef CONFIG_KASAN_GENERIC #define KASAN_SHADOW_END ((UL(1) << (64 - KASAN_SHADOW_SCALE_SHIFT)) + KAS= AN_SHADOW_OFFSET) +#else +#define KASAN_SHADOW_END KASAN_SHADOW_OFFSET +#endif #define _KASAN_SHADOW_START(va) (KASAN_SHADOW_END - (UL(1) << ((va) - KASA= N_SHADOW_SCALE_SHIFT))) #define KASAN_SHADOW_START _KASAN_SHADOW_START(vabits_actual) #define PAGE_END KASAN_SHADOW_START diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c index d541ce45daeb..dc2de12c4f26 100644 --- a/arch/arm64/mm/kasan_init.c +++ b/arch/arm64/mm/kasan_init.c @@ -198,8 +198,11 @@ static bool __init root_level_aligned(u64 addr) /* The early shadow maps everything to a single page of zeroes */ asmlinkage void __init kasan_early_init(void) { - BUILD_BUG_ON(KASAN_SHADOW_OFFSET !=3D - KASAN_SHADOW_END - (1UL << (64 - KASAN_SHADOW_SCALE_SHIFT))); + if (IS_ENABLED(CONFIG_KASAN_GENERIC)) + BUILD_BUG_ON(KASAN_SHADOW_OFFSET !=3D + KASAN_SHADOW_END - (1UL << (64 - KASAN_SHADOW_SCALE_SHIFT))); + else + BUILD_BUG_ON(KASAN_SHADOW_OFFSET !=3D KASAN_SHADOW_END); BUILD_BUG_ON(!IS_ALIGNED(_KASAN_SHADOW_START(VA_BITS), SHADOW_ALIGN)); BUILD_BUG_ON(!IS_ALIGNED(_KASAN_SHADOW_START(VA_BITS_MIN), SHADOW_ALIGN)); BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, SHADOW_ALIGN)); diff --git a/include/linux/kasan.h b/include/linux/kasan.h index 890011071f2b..b396feca714f 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -61,8 +61,14 @@ int kasan_populate_early_shadow(const void *shadow_start, #ifndef kasan_mem_to_shadow static inline void *kasan_mem_to_shadow(const void *addr) { - return (void *)((unsigned long)addr >> KASAN_SHADOW_SCALE_SHIFT) - + KASAN_SHADOW_OFFSET; + void *scaled; + + if (IS_ENABLED(CONFIG_KASAN_GENERIC)) + scaled =3D (void *)((unsigned long)addr >> KASAN_SHADOW_SCALE_SHIFT); + else + scaled =3D (void *)((long)addr >> KASAN_SHADOW_SCALE_SHIFT); + + return KASAN_SHADOW_OFFSET + scaled; } #endif =20 diff --git a/mm/kasan/report.c b/mm/kasan/report.c index 62c01b4527eb..50d487a0687a 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c @@ -642,11 +642,39 @@ void kasan_non_canonical_hook(unsigned long addr) const char *bug_type; =20 /* - * All addresses that came as a result of the memory-to-shadow mapping - * (even for bogus pointers) must be >=3D KASAN_SHADOW_OFFSET. + * For Generic KASAN, kasan_mem_to_shadow() uses the logical right shift + * and never overflows with the chosen KASAN_SHADOW_OFFSET values (on + * both x86 and arm64). Thus, the possible shadow addresses (even for + * bogus pointers) belong to a single contiguous region that is the + * result of kasan_mem_to_shadow() applied to the whole address space. */ - if (addr < KASAN_SHADOW_OFFSET) - return; + if (IS_ENABLED(CONFIG_KASAN_GENERIC)) { + if (addr < (unsigned long)kasan_mem_to_shadow((void *)(0UL)) || + addr > (unsigned long)kasan_mem_to_shadow((void *)(~0UL))) + return; + } + + /* + * For Software Tag-Based KASAN, kasan_mem_to_shadow() uses the + * arithmetic shift. Normally, this would make checking for a possible + * shadow address complicated, as the shadow address computation + * operation would overflow only for some memory addresses. However, due + * to the chosen KASAN_SHADOW_OFFSET values and the fact the + * kasan_mem_to_shadow() only operates on pointers with the tag reset, + * the overflow always happens. + * + * For arm64, the top byte of the pointer gets reset to 0xFF. Thus, the + * possible shadow addresses belong to a region that is the result of + * kasan_mem_to_shadow() applied to the memory range + * [0xFF000000000000, 0xFFFFFFFFFFFFFFFF]. Despite the overflow, the + * resulting possible shadow region is contiguous, as the overflow + * happens for both 0xFF000000000000 and 0xFFFFFFFFFFFFFFFF. + */ + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS) && IS_ENABLED(CONFIG_ARM64)) { + if (addr < (unsigned long)kasan_mem_to_shadow((void *)(0xFFUL << 56)) || + addr > (unsigned long)kasan_mem_to_shadow((void *)(~0UL))) + return; + } =20 orig_addr =3D (unsigned long)kasan_shadow_to_mem((void *)addr); =20 diff --git a/scripts/gdb/linux/kasan.py b/scripts/gdb/linux/kasan.py index 56730b3fde0b..fca39968d308 100644 --- a/scripts/gdb/linux/kasan.py +++ b/scripts/gdb/linux/kasan.py @@ -8,6 +8,7 @@ =20 import gdb from linux import constants, mm +from ctypes import c_int64 as s64 =20 def help(): t =3D """Usage: lx-kasan_mem_to_shadow [Hex memory addr] @@ -39,6 +40,8 @@ class KasanMemToShadow(gdb.Command): else: help() def kasan_mem_to_shadow(self, addr): + if constants.CONFIG_KASAN_SW_TAGS: + addr =3D s64(addr) return (addr >> self.p_ops.KASAN_SHADOW_SCALE_SHIFT) + self.p_ops.= KASAN_SHADOW_OFFSET =20 KasanMemToShadow() diff --git a/scripts/gdb/linux/mm.py b/scripts/gdb/linux/mm.py index 7571aebbe650..2e63f3dedd53 100644 --- a/scripts/gdb/linux/mm.py +++ b/scripts/gdb/linux/mm.py @@ -110,12 +110,13 @@ class aarch64_page_ops(): self.KERNEL_END =3D gdb.parse_and_eval("_end") =20 if constants.LX_CONFIG_KASAN_GENERIC or constants.LX_CONFIG_KASAN_= SW_TAGS: + self.KASAN_SHADOW_OFFSET =3D constants.LX_CONFIG_KASAN_SHADOW_= OFFSET if constants.LX_CONFIG_KASAN_GENERIC: self.KASAN_SHADOW_SCALE_SHIFT =3D 3 + self.KASAN_SHADOW_END =3D (1 << (64 - self.KASAN_SHADOW_SC= ALE_SHIFT)) + self.KASAN_SHADOW_OFFSET else: self.KASAN_SHADOW_SCALE_SHIFT =3D 4 - self.KASAN_SHADOW_OFFSET =3D constants.LX_CONFIG_KASAN_SHADOW_= OFFSET - self.KASAN_SHADOW_END =3D (1 << (64 - self.KASAN_SHADOW_SCALE_= SHIFT)) + self.KASAN_SHADOW_OFFSET + self.KASAN_SHADOW_END =3D self.KASAN_SHADOW_OFFSET self.PAGE_END =3D self.KASAN_SHADOW_END - (1 << (self.vabits_a= ctual - self.KASAN_SHADOW_SCALE_SHIFT)) else: self.PAGE_END =3D self._PAGE_END(self.VA_BITS_MIN) --=20 2.50.1 From nobody Fri Oct 3 20:23:07 2025 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7D0E2285C9F; 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a="68970308" X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="68970308" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:26:15 -0700 X-CSE-ConnectionGUID: +L18yj8dSzOfEZlF7N6ftA== X-CSE-MsgGUID: jAlCsbyqSiWfjyrRW8QvcQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="169779897" Received: from bergbenj-mobl1.ger.corp.intel.com (HELO wieczorr-mobl1.intel.com) ([10.245.245.6]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:25:53 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 02/19] kasan: sw_tags: Support tag widths less than 8 bits Date: Mon, 25 Aug 2025 22:24:27 +0200 Message-ID: <83955e7079c0fb9c11169d25adc6303f0c66c1ec.1756151769.git.maciej.wieczor-retman@intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Samuel Holland Allow architectures to override KASAN_TAG_KERNEL in asm/kasan.h. This is needed on RISC-V, which supports 57-bit virtual addresses and 7-bit pointer tags. For consistency, move the arm64 MTE definition of KASAN_TAG_MIN to asm/kasan.h, since it is also architecture-dependent; RISC-V's equivalent extension is expected to support 7-bit hardware memory tags. Reviewed-by: Andrey Konovalov Signed-off-by: Samuel Holland Signed-off-by: Maciej Wieczor-Retman --- arch/arm64/include/asm/kasan.h | 6 ++++-- arch/arm64/include/asm/uaccess.h | 1 + include/linux/kasan-tags.h | 13 ++++++++----- 3 files changed, 13 insertions(+), 7 deletions(-) diff --git a/arch/arm64/include/asm/kasan.h b/arch/arm64/include/asm/kasan.h index e1b57c13f8a4..4ab419df8b93 100644 --- a/arch/arm64/include/asm/kasan.h +++ b/arch/arm64/include/asm/kasan.h @@ -6,8 +6,10 @@ =20 #include #include -#include -#include + +#ifdef CONFIG_KASAN_HW_TAGS +#define KASAN_TAG_MIN 0xF0 /* minimum value for random tags */ +#endif =20 #define arch_kasan_set_tag(addr, tag) __tag_set(addr, tag) #define arch_kasan_reset_tag(addr) __tag_reset(addr) diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uacc= ess.h index 5b91803201ef..f890dadc7b4e 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -22,6 +22,7 @@ #include #include #include +#include #include #include #include diff --git a/include/linux/kasan-tags.h b/include/linux/kasan-tags.h index 4f85f562512c..e07c896f95d3 100644 --- a/include/linux/kasan-tags.h +++ b/include/linux/kasan-tags.h @@ -2,13 +2,16 @@ #ifndef _LINUX_KASAN_TAGS_H #define _LINUX_KASAN_TAGS_H =20 +#include + +#ifndef KASAN_TAG_KERNEL #define KASAN_TAG_KERNEL 0xFF /* native kernel pointers tag */ -#define KASAN_TAG_INVALID 0xFE /* inaccessible memory tag */ -#define KASAN_TAG_MAX 0xFD /* maximum value for random tags */ +#endif + +#define KASAN_TAG_INVALID (KASAN_TAG_KERNEL - 1) /* inaccessible memory ta= g */ +#define KASAN_TAG_MAX (KASAN_TAG_KERNEL - 2) /* maximum value for random = tags */ =20 -#ifdef CONFIG_KASAN_HW_TAGS -#define KASAN_TAG_MIN 0xF0 /* minimum value for random tags */ -#else +#ifndef KASAN_TAG_MIN #define KASAN_TAG_MIN 0x00 /* minimum value for random tags */ #endif =20 --=20 2.50.1 From nobody Fri Oct 3 20:23:07 2025 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9B962288511; 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a="68970348" X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="68970348" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:26:34 -0700 X-CSE-ConnectionGUID: iIqUDEsESZCpnMn6v7RjVA== X-CSE-MsgGUID: 2PEh8pueQKehSA2GUwmUug== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="169779925" Received: from bergbenj-mobl1.ger.corp.intel.com (HELO wieczorr-mobl1.intel.com) ([10.245.245.6]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:26:15 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 03/19] kasan: Fix inline mode for x86 tag-based mode Date: Mon, 25 Aug 2025 22:24:28 +0200 Message-ID: <98d2c875da80331a51a5c61e8a67ca43fc57cbd3.1756151769.git.maciej.wieczor-retman@intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The LLVM compiler uses hwasan-instrument-with-calls parameter to setup inline or outline mode in tag-based KASAN. If zeroed, it means the instrumentation implementation will be pasted into each relevant location along with KASAN related constants during compilation. If set to one all function instrumentation will be done with function calls instead. The default hwasan-instrument-with-calls value for the x86 architecture in the compiler is "1", which is not true for other architectures. Because of this, enabling inline mode in software tag-based KASAN doesn't work on x86 as the kernel script doesn't zero out the parameter and always sets up the outline mode. Explicitly zero out hwasan-instrument-with-calls when enabling inline mode in tag-based KASAN. Signed-off-by: Maciej Wieczor-Retman Reviewed-by: Andrey Konovalov --- Changelog v3: - Add this patch to the series. scripts/Makefile.kasan | 3 +++ 1 file changed, 3 insertions(+) diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan index 693dbbebebba..2c7be96727ac 100644 --- a/scripts/Makefile.kasan +++ b/scripts/Makefile.kasan @@ -76,8 +76,11 @@ CFLAGS_KASAN :=3D -fsanitize=3Dkernel-hwaddress RUSTFLAGS_KASAN :=3D -Zsanitizer=3Dkernel-hwaddress \ -Zsanitizer-recover=3Dkernel-hwaddress =20 +# LLVM sets hwasan-instrument-with-calls to 1 on x86 by default. 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d="scan'208";a="169780102" Received: from bergbenj-mobl1.ger.corp.intel.com (HELO wieczorr-mobl1.intel.com) ([10.245.245.6]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:26:35 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 04/19] x86: Add arch specific kasan functions Date: Mon, 25 Aug 2025 22:24:29 +0200 Message-ID: <7cb9edae06aeaf8c69013a89f1fd13a9e1531d54.1756151769.git.maciej.wieczor-retman@intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" KASAN's software tag-based mode needs multiple macros/functions to handle tag and pointer interactions - to set, retrieve and reset tags from the top bits of a pointer. Mimic functions currently used by arm64 but change the tag's position to bits [60:57] in the pointer. Signed-off-by: Maciej Wieczor-Retman Acked-by: Andrey Konovalov --- Changelog v4: - Rewrite __tag_set() without pointless casts and make it more readable. Changelog v3: - Reorder functions so that __tag_*() etc are above the arch_kasan_*() ones. - Remove CONFIG_KASAN condition from __tag_set() arch/x86/include/asm/kasan.h | 36 ++++++++++++++++++++++++++++++++++-- 1 file changed, 34 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/kasan.h b/arch/x86/include/asm/kasan.h index d7e33c7f096b..1963eb2fcff3 100644 --- a/arch/x86/include/asm/kasan.h +++ b/arch/x86/include/asm/kasan.h @@ -3,6 +3,8 @@ #define _ASM_X86_KASAN_H =20 #include +#include +#include #define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL) #define KASAN_SHADOW_SCALE_SHIFT 3 =20 @@ -24,8 +26,37 @@ KASAN_SHADOW_SCALE_SHIFT))) =20 #ifndef __ASSEMBLER__ +#include +#include +#include + +#ifdef CONFIG_KASAN_SW_TAGS + +#define __tag_shifted(tag) FIELD_PREP(GENMASK_ULL(60, 57), tag) +#define __tag_reset(addr) (sign_extend64((u64)(addr), 56)) +#define __tag_get(addr) ((u8)FIELD_GET(GENMASK_ULL(60, 57), (u64)addr)) +#else +#define __tag_shifted(tag) 0UL +#define __tag_reset(addr) (addr) +#define __tag_get(addr) 0 +#endif /* CONFIG_KASAN_SW_TAGS */ + +static inline void *__tag_set(const void *__addr, u8 tag) +{ + u64 addr =3D (u64)__addr; + + addr &=3D ~__tag_shifted(KASAN_TAG_MASK); + addr |=3D __tag_shifted(tag); + + return (void *)addr; +} + +#define arch_kasan_set_tag(addr, tag) __tag_set(addr, tag) +#define arch_kasan_reset_tag(addr) __tag_reset(addr) +#define arch_kasan_get_tag(addr) __tag_get(addr) =20 #ifdef CONFIG_KASAN + void __init kasan_early_init(void); void __init kasan_init(void); void __init kasan_populate_shadow_for_vaddr(void *va, size_t size, int nid= ); @@ -34,8 +65,9 @@ static inline void kasan_early_init(void) { } static inline void kasan_init(void) { } static inline void kasan_populate_shadow_for_vaddr(void *va, size_t size, int nid) { } -#endif =20 -#endif +#endif /* CONFIG_KASAN */ + +#endif /* __ASSEMBLER__ */ =20 #endif --=20 2.50.1 From nobody Fri Oct 3 20:23:07 2025 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8887328D850; 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a="68970455" X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="68970455" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:27:19 -0700 X-CSE-ConnectionGUID: aQ202IPqRcWU0JmqPLmwhQ== X-CSE-MsgGUID: fhmF8QYeQ8GO7LAXlViwDA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="169780311" Received: from bergbenj-mobl1.ger.corp.intel.com (HELO wieczorr-mobl1.intel.com) ([10.245.245.6]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:26:57 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 05/19] kasan: arm64: x86: Make special tags arch specific Date: Mon, 25 Aug 2025 22:24:30 +0200 Message-ID: <7a85ceb0918c6b204078e6d479b85fef6a6c1768.1756151769.git.maciej.wieczor-retman@intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" KASAN's tag-based mode defines multiple special tag values. They're reserved for: - Native kernel value. On arm64 it's 0xFF and it causes an early return in the tag checking function. - Invalid value. 0xFE marks an area as freed / unallocated. It's also the value that is used to initialize regions of shadow memory. - Max value. 0xFD is the highest value that can be randomly generated for a new tag. Metadata macro is also defined: - Tag width equal to 8. Tag-based mode on x86 is going to use 4 bit wide tags so all the above values need to be changed accordingly. Make native kernel tag arch specific for x86 and arm64. Replace hardcoded kernel tag value and tag width with macros in KASAN's non-arch specific code. Signed-off-by: Maciej Wieczor-Retman --- Changelog v5: - Move KASAN_TAG_MIN to the arm64 kasan-tags.h for the hardware KASAN mode case. Changelog v4: - Move KASAN_TAG_MASK to kasan-tags.h. Changelog v2: - Remove risc-v from the patch. MAINTAINERS | 2 +- arch/arm64/include/asm/kasan-tags.h | 13 +++++++++++++ arch/arm64/include/asm/kasan.h | 4 ---- arch/x86/include/asm/kasan-tags.h | 9 +++++++++ include/linux/kasan-tags.h | 10 +++++++++- include/linux/kasan.h | 4 +++- include/linux/mm.h | 6 +++--- include/linux/mmzone.h | 1 - include/linux/page-flags-layout.h | 9 +-------- 9 files changed, 39 insertions(+), 19 deletions(-) create mode 100644 arch/arm64/include/asm/kasan-tags.h create mode 100644 arch/x86/include/asm/kasan-tags.h diff --git a/MAINTAINERS b/MAINTAINERS index fed6cd812d79..788532771832 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -13176,7 +13176,7 @@ L: kasan-dev@googlegroups.com S: Maintained B: https://bugzilla.kernel.org/buglist.cgi?component=3DSanitizers&product= =3DMemory%20Management F: Documentation/dev-tools/kasan.rst -F: arch/*/include/asm/*kasan.h +F: arch/*/include/asm/*kasan*.h F: arch/*/mm/kasan_init* F: include/linux/kasan*.h F: lib/Kconfig.kasan diff --git a/arch/arm64/include/asm/kasan-tags.h b/arch/arm64/include/asm/k= asan-tags.h new file mode 100644 index 000000000000..152465d03508 --- /dev/null +++ b/arch/arm64/include/asm/kasan-tags.h @@ -0,0 +1,13 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_KASAN_TAGS_H +#define __ASM_KASAN_TAGS_H + +#define KASAN_TAG_KERNEL 0xFF /* native kernel pointers tag */ + +#define KASAN_TAG_WIDTH 8 + +#ifdef CONFIG_KASAN_HW_TAGS +#define KASAN_TAG_MIN 0xF0 /* minimum value for random tags */ +#endif + +#endif /* ASM_KASAN_TAGS_H */ diff --git a/arch/arm64/include/asm/kasan.h b/arch/arm64/include/asm/kasan.h index 4ab419df8b93..d2841e0fb908 100644 --- a/arch/arm64/include/asm/kasan.h +++ b/arch/arm64/include/asm/kasan.h @@ -7,10 +7,6 @@ #include #include =20 -#ifdef CONFIG_KASAN_HW_TAGS -#define KASAN_TAG_MIN 0xF0 /* minimum value for random tags */ -#endif - #define arch_kasan_set_tag(addr, tag) __tag_set(addr, tag) #define arch_kasan_reset_tag(addr) __tag_reset(addr) #define arch_kasan_get_tag(addr) __tag_get(addr) diff --git a/arch/x86/include/asm/kasan-tags.h b/arch/x86/include/asm/kasan= -tags.h new file mode 100644 index 000000000000..68ba385bc75c --- /dev/null +++ b/arch/x86/include/asm/kasan-tags.h @@ -0,0 +1,9 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_KASAN_TAGS_H +#define __ASM_KASAN_TAGS_H + +#define KASAN_TAG_KERNEL 0xF /* native kernel pointers tag */ + +#define KASAN_TAG_WIDTH 4 + +#endif /* ASM_KASAN_TAGS_H */ diff --git a/include/linux/kasan-tags.h b/include/linux/kasan-tags.h index e07c896f95d3..fe80fa8f3315 100644 --- a/include/linux/kasan-tags.h +++ b/include/linux/kasan-tags.h @@ -2,7 +2,15 @@ #ifndef _LINUX_KASAN_TAGS_H #define _LINUX_KASAN_TAGS_H =20 -#include +#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS) +#include +#endif + +#ifndef KASAN_TAG_WIDTH +#define KASAN_TAG_WIDTH 0 +#endif + +#define KASAN_TAG_MASK ((1UL << KASAN_TAG_WIDTH) - 1) =20 #ifndef KASAN_TAG_KERNEL #define KASAN_TAG_KERNEL 0xFF /* native kernel pointers tag */ diff --git a/include/linux/kasan.h b/include/linux/kasan.h index b396feca714f..54481f8c30c5 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -40,7 +40,9 @@ typedef unsigned int __bitwise kasan_vmalloc_flags_t; =20 #ifdef CONFIG_KASAN_SW_TAGS /* This matches KASAN_TAG_INVALID. */ -#define KASAN_SHADOW_INIT 0xFE +#ifndef KASAN_SHADOW_INIT +#define KASAN_SHADOW_INIT KASAN_TAG_INVALID +#endif #else #define KASAN_SHADOW_INIT 0 #endif diff --git a/include/linux/mm.h b/include/linux/mm.h index 1ae97a0b8ec7..bb494cb1d5af 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1692,7 +1692,7 @@ static inline u8 page_kasan_tag(const struct page *pa= ge) =20 if (kasan_enabled()) { tag =3D (page->flags >> KASAN_TAG_PGSHIFT) & KASAN_TAG_MASK; - tag ^=3D 0xff; + tag ^=3D KASAN_TAG_KERNEL; } =20 return tag; @@ -1705,7 +1705,7 @@ static inline void page_kasan_tag_set(struct page *pa= ge, u8 tag) if (!kasan_enabled()) return; =20 - tag ^=3D 0xff; + tag ^=3D KASAN_TAG_KERNEL; old_flags =3D READ_ONCE(page->flags); do { flags =3D old_flags; @@ -1724,7 +1724,7 @@ static inline void page_kasan_tag_reset(struct page *= page) =20 static inline u8 page_kasan_tag(const struct page *page) { - return 0xff; + return KASAN_TAG_KERNEL; 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a="68970503" X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="68970503" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:27:38 -0700 X-CSE-ConnectionGUID: 88rMVBboREqinEplSn4Mdw== X-CSE-MsgGUID: 3rIVdVdjQ/akH62ekpclSQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="169780355" Received: from bergbenj-mobl1.ger.corp.intel.com (HELO wieczorr-mobl1.intel.com) ([10.245.245.6]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:27:19 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 06/19] x86: Reset tag for virtual to physical address conversions Date: Mon, 25 Aug 2025 22:24:31 +0200 Message-ID: <462dc78d4d986007e82c12ad57bb6b11f85b19a1.1756151769.git.maciej.wieczor-retman@intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Any place where pointer arithmetic is used to convert a virtual address into a physical one can raise errors if the virtual address is tagged. Reset the pointer's tag by sign extending the tag bits in macros that do pointer arithmetic in address conversions. There will be no change in compiled code with KASAN disabled since the compiler will optimize the __tag_reset() out. Signed-off-by: Maciej Wieczor-Retman --- Changelog v5: - Move __tag_reset() calls into __phys_addr_nodebug() and __virt_addr_valid() instead of calling it on the arguments of higher level functions. Changelog v4: - Simplify page_to_virt() by removing pointless casts. - Remove change in __is_canonical_address() because it's taken care of in a later patch due to a LAM compatible definition of canonical. arch/x86/include/asm/page.h | 8 ++++++++ arch/x86/include/asm/page_64.h | 1 + arch/x86/mm/physaddr.c | 2 ++ 3 files changed, 11 insertions(+) diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h index 9265f2fca99a..bcf5cad3da36 100644 --- a/arch/x86/include/asm/page.h +++ b/arch/x86/include/asm/page.h @@ -7,6 +7,7 @@ #ifdef __KERNEL__ =20 #include +#include =20 #ifdef CONFIG_X86_64 #include @@ -65,6 +66,13 @@ static inline void copy_user_page(void *to, void *from, = unsigned long vaddr, * virt_to_page(kaddr) returns a valid pointer if and only if * virt_addr_valid(kaddr) returns true. */ + +#ifdef CONFIG_KASAN_SW_TAGS +#define page_to_virt(x) ({ \ + void *__addr =3D __va(page_to_pfn((struct page *)x) << PAGE_SHIFT); \ + __tag_set(__addr, page_kasan_tag(x)); \ +}) +#endif #define virt_to_page(kaddr) pfn_to_page(__pa(kaddr) >> PAGE_SHIFT) extern bool __virt_addr_valid(unsigned long kaddr); #define virt_addr_valid(kaddr) __virt_addr_valid((unsigned long) (kaddr)) diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h index 015d23f3e01f..b18fef43dd34 100644 --- a/arch/x86/include/asm/page_64.h +++ b/arch/x86/include/asm/page_64.h @@ -21,6 +21,7 @@ extern unsigned long direct_map_physmem_end; =20 static __always_inline unsigned long __phys_addr_nodebug(unsigned long x) { + x =3D __tag_reset(x); unsigned long y =3D x - __START_KERNEL_map; =20 /* use the carry flag to determine if x was < __START_KERNEL_map */ diff --git a/arch/x86/mm/physaddr.c b/arch/x86/mm/physaddr.c index fc3f3d3e2ef2..d6aa3589c798 100644 --- a/arch/x86/mm/physaddr.c +++ b/arch/x86/mm/physaddr.c @@ -14,6 +14,7 @@ #ifdef CONFIG_DEBUG_VIRTUAL unsigned long __phys_addr(unsigned long x) { + x =3D __tag_reset(x); unsigned long y =3D x - __START_KERNEL_map; =20 /* use the carry flag to determine if x was < __START_KERNEL_map */ @@ -46,6 +47,7 @@ EXPORT_SYMBOL(__phys_addr_symbol); =20 bool __virt_addr_valid(unsigned long x) { + x =3D __tag_reset(x); 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25 Aug 2025 13:27:38 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 07/19] mm: x86: Untag addresses in EXECMEM_ROX related pointer arithmetic Date: Mon, 25 Aug 2025 22:24:32 +0200 Message-ID: X-Mailer: git-send-email 2.50.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" ARCH_HAS_EXECMEM_ROX was re-enabled in x86 at Linux 6.14 release. Related code has multiple spots where page virtual addresses end up used as arguments in arithmetic operations. Combined with enabled tag-based KASAN it can result in pointers that don't point where they should or logical operations not giving expected results. vm_reset_perms() calculates range's start and end addresses using min() and max() functions. To do that it compares pointers but some are not tagged - addr variable is, start and end variables aren't. within() and within_range() can receive tagged addresses which get compared to untagged start and end variables. Reset tags in addresses used as function arguments in min(), max(), within(). execmem_cache_add() adds tagged pointers to a maple tree structure, which then are incorrectly compared when walking the tree. That results in different pointers being returned later and page permission violation errors panicking the kernel. Reset tag of the address range inserted into the maple tree inside execmem_cache_add(). Signed-off-by: Maciej Wieczor-Retman --- Changelog v5: - Remove the within_range() change. - arch_kasan_reset_tag -> kasan_reset_tag. Changelog v4: - Add patch to the series. mm/execmem.c | 2 +- mm/vmalloc.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/execmem.c b/mm/execmem.c index 0822305413ec..f7b7bdacaec5 100644 --- a/mm/execmem.c +++ b/mm/execmem.c @@ -186,7 +186,7 @@ static DECLARE_WORK(execmem_cache_clean_work, execmem_c= ache_clean); static int execmem_cache_add_locked(void *ptr, size_t size, gfp_t gfp_mask) { struct maple_tree *free_areas =3D &execmem_cache.free_areas; - unsigned long addr =3D (unsigned long)ptr; + unsigned long addr =3D (unsigned long)kasan_reset_tag(ptr); MA_STATE(mas, free_areas, addr - 1, addr + 1); unsigned long lower, upper; void *area =3D NULL; diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 6dbcdceecae1..c93893fb8dd4 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -3322,7 +3322,7 @@ static void vm_reset_perms(struct vm_struct *area) * the vm_unmap_aliases() flush includes the direct map. */ for (i =3D 0; i < area->nr_pages; i +=3D 1U << page_order) { - unsigned long addr =3D (unsigned long)page_address(area->pages[i]); 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charset="utf-8" Calculating page offset returns a pointer without a tag. When comparing the calculated offset to a tagged page pointer an error is raised because they are not equal. Change pointer comparisons to physical address comparisons as to avoid issues with tagged pointers that pointer arithmetic would create. Open code pte_offset_kernel(), pmd_offset(), pud_offset() and p4d_offset(). Because one parameter is always zero and the rest of the function insides are enclosed inside __va(), removing that layer lowers the complexity of final assembly. Signed-off-by: Maciej Wieczor-Retman --- Changelog v2: - Open code *_offset() to avoid it's internal __va(). arch/x86/mm/init_64.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 76e33bd7c556..51a247e258b1 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -251,7 +251,10 @@ static p4d_t *fill_p4d(pgd_t *pgd, unsigned long vaddr) if (pgd_none(*pgd)) { p4d_t *p4d =3D (p4d_t *)spp_getpage(); pgd_populate(&init_mm, pgd, p4d); - if (p4d !=3D p4d_offset(pgd, 0)) + + if (__pa(p4d) !=3D (pgtable_l5_enabled() ? + __pa(pgd) : + (unsigned long)pgd_val(*pgd) & PTE_PFN_MASK)) printk(KERN_ERR "PAGETABLE BUG #00! %p <-> %p\n", p4d, p4d_offset(pgd, 0)); } @@ -263,7 +266,7 @@ static pud_t *fill_pud(p4d_t *p4d, unsigned long vaddr) if (p4d_none(*p4d)) { pud_t *pud =3D (pud_t *)spp_getpage(); p4d_populate(&init_mm, p4d, pud); - if (pud !=3D pud_offset(p4d, 0)) + if (__pa(pud) !=3D (p4d_val(*p4d) & p4d_pfn_mask(*p4d))) printk(KERN_ERR "PAGETABLE BUG #01! %p <-> %p\n", pud, pud_offset(p4d, 0)); 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a="68970649" X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="68970649" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:28:39 -0700 X-CSE-ConnectionGUID: ZdrF+c9oTnqXBOaj3/bbCw== X-CSE-MsgGUID: b88EEwdzTV2GCqGXKxP8lQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="169780469" Received: from bergbenj-mobl1.ger.corp.intel.com (HELO wieczorr-mobl1.intel.com) ([10.245.245.6]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:28:20 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 09/19] x86: KASAN raw shadow memory PTE init Date: Mon, 25 Aug 2025 22:24:34 +0200 Message-ID: <9a7958543abababa30d534c44ba2f26d6bd692d6.1756151769.git.maciej.wieczor-retman@intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" In KASAN's generic mode the default value in shadow memory is zero. During initialization of shadow memory pages they are allocated and zeroed. In KASAN's tag-based mode the default tag for the arm64 architecture is 0xFE which corresponds to any memory that should not be accessed. On x86 (where tags are 4-bit wide instead of 8-bit wide) that tag is 0xE so during the initializations all the bytes in shadow memory pages should be filled with it. Use memblock_alloc_try_nid_raw() instead of memblock_alloc_try_nid() to avoid zeroing out the memory so it can be set with the KASAN invalid tag. Signed-off-by: Maciej Wieczor-Retman --- Changelog v2: - Remove dense mode references, use memset() instead of kasan_poison(). arch/x86/mm/kasan_init_64.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c index 0539efd0d216..e8a451cafc8c 100644 --- a/arch/x86/mm/kasan_init_64.c +++ b/arch/x86/mm/kasan_init_64.c @@ -34,6 +34,18 @@ static __init void *early_alloc(size_t size, int nid, bo= ol should_panic) return ptr; } =20 +static __init void *early_raw_alloc(size_t size, int nid, bool should_pani= c) +{ + void *ptr =3D memblock_alloc_try_nid_raw(size, size, + __pa(MAX_DMA_ADDRESS), MEMBLOCK_ALLOC_ACCESSIBLE, nid); + + if (!ptr && should_panic) + panic("%pS: Failed to allocate page, nid=3D%d from=3D%lx\n", + (void *)_RET_IP_, nid, __pa(MAX_DMA_ADDRESS)); + + return ptr; +} + static void __init kasan_populate_pmd(pmd_t *pmd, unsigned long addr, unsigned long end, int nid) { @@ -63,8 +75,9 @@ static void __init kasan_populate_pmd(pmd_t *pmd, unsigne= d long addr, if (!pte_none(*pte)) continue; =20 - p =3D early_alloc(PAGE_SIZE, nid, true); - entry =3D pfn_pte(PFN_DOWN(__pa(p)), PAGE_KERNEL); + p =3D early_raw_alloc(PAGE_SIZE, nid, true); + memset(p, PAGE_SIZE, KASAN_SHADOW_INIT); + entry =3D pfn_pte(PFN_DOWN(__pa_nodebug(p)), PAGE_KERNEL); set_pte_at(&init_mm, addr, pte, entry); } while (pte++, addr +=3D PAGE_SIZE, addr !=3D end); } @@ -436,7 +449,7 @@ void __init kasan_init(void) * it may contain some garbage. 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charset="utf-8" For an address to be canonical it has to have its top bits equal to each other. The number of bits depends on the paging level and whether they're supposed to be ones or zeroes depends on whether the address points to kernel or user space. With Linear Address Masking (LAM) enabled, the definition of linear address canonicality is modified. Not all of the previously required bits need to be equal, only the first and last from the previously equal bitmask. So for example a 5-level paging kernel address needs to have bits [63] and [56] set. Add separate __canonical_address() implementation for CONFIG_KASAN_SW_TAGS since it's the only thing right now that enables LAM for kernel addresses (LAM_SUP bit in CR4). Signed-off-by: Maciej Wieczor-Retman --- Changelog v4: - Add patch to the series. arch/x86/include/asm/page.h | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h index bcf5cad3da36..a83f23a71f35 100644 --- a/arch/x86/include/asm/page.h +++ b/arch/x86/include/asm/page.h @@ -82,10 +82,20 @@ static __always_inline void *pfn_to_kaddr(unsigned long= pfn) return __va(pfn << PAGE_SHIFT); } =20 +/* + * CONFIG_KASAN_SW_TAGS requires LAM which changes the canonicality checks. + */ +#ifdef CONFIG_KASAN_SW_TAGS +static __always_inline u64 __canonical_address(u64 vaddr, u8 vaddr_bits) +{ + return (vaddr | BIT_ULL(63) | BIT_ULL(vaddr_bits - 1)); +} +#else static __always_inline u64 __canonical_address(u64 vaddr, u8 vaddr_bits) { return ((s64)vaddr << (64 - vaddr_bits)) >> (64 - vaddr_bits); } +#endif =20 static __always_inline u64 __is_canonical_address(u64 vaddr, u8 vaddr_bits) { --=20 2.50.1 From nobody Fri Oct 3 20:23:07 2025 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0E8A62248A8; 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a="68970761" X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="68970761" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:29:23 -0700 X-CSE-ConnectionGUID: 2iU/MAdEQzuCmnajWPCpwA== X-CSE-MsgGUID: Li6ndXn4Q1+50YJZ69xiow== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="169780561" Received: from bergbenj-mobl1.ger.corp.intel.com (HELO wieczorr-mobl1.intel.com) ([10.245.245.6]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:29:02 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 11/19] x86: LAM initialization Date: Mon, 25 Aug 2025 22:24:36 +0200 Message-ID: X-Mailer: git-send-email 2.50.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" To make use of KASAN's tag based mode on x86, Linear Address Masking (LAM) needs to be enabled. To do that the 28th bit in CR4 has to be set. Set the bit in early memory initialization. When launching secondary CPUs the LAM bit gets lost. To avoid this add it in a mask in head_64.S. The bitmask permits some bits of CR4 to pass from the primary CPU to the secondary CPUs without being cleared. Signed-off-by: Maciej Wieczor-Retman --- arch/x86/kernel/head_64.S | 3 +++ arch/x86/mm/init.c | 3 +++ 2 files changed, 6 insertions(+) diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 3e9b3a3bd039..18ca77daa481 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -209,6 +209,9 @@ SYM_INNER_LABEL(common_startup_64, SYM_L_LOCAL) * there will be no global TLB entries after the execution." */ movl $(X86_CR4_PAE | X86_CR4_LA57), %edx +#ifdef CONFIG_ADDRESS_MASKING + orl $X86_CR4_LAM_SUP, %edx +#endif #ifdef CONFIG_X86_MCE /* * Preserve CR4.MCE if the kernel will enable #MC support. diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index bb57e93b4caf..756bd96c3b8b 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -763,6 +763,9 @@ void __init init_mem_mapping(void) probe_page_size_mask(); setup_pcid(); =20 + if (boot_cpu_has(X86_FEATURE_LAM) && IS_ENABLED(CONFIG_KASAN_SW_TAGS)) + cr4_set_bits_and_update_boot(X86_CR4_LAM_SUP); + #ifdef CONFIG_X86_64 end =3D max_pfn << PAGE_SHIFT; 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charset="utf-8" 8 byte minimal SLAB alignment interferes with KASAN's granularity of 16 bytes. It causes a lot of out-of-bounds errors for unaligned 8 byte allocations. Compared to a kernel with KASAN disabled, the memory footprint increases because all kmalloc-8 allocations now are realized as kmalloc-16, which has twice the object size. But more meaningfully, when compared to a kernel with generic KASAN enabled, there is no difference. Because of redzones in generic KASAN, kmalloc-8' and kmalloc-16' object size is the same (48 bytes). So changing the minimal SLAB alignment of the tag-based mode doesn't have any negative impact when compared to the other software KASAN mode. Adjust x86 minimal SLAB alignment to match KASAN granularity size. Signed-off-by: Maciej Wieczor-Retman Reviewed-by: Andrey Konovalov --- Changelog v4: - Extend the patch message with some more context and impact information. 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25 Aug 2025 13:30:07 -0700 X-CSE-ConnectionGUID: vVb0osiSTzynXkLiboYB/w== X-CSE-MsgGUID: DrJ+CdCFQni2g9dVLCwjCw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="169780722" Received: from bergbenj-mobl1.ger.corp.intel.com (HELO wieczorr-mobl1.intel.com) ([10.245.245.6]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:29:44 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 13/19] kasan: x86: Handle int3 for inline KASAN reports Date: Mon, 25 Aug 2025 22:24:38 +0200 Message-ID: <36c0e5e9d875addc42a73168b8090144c327ec9f.1756151769.git.maciej.wieczor-retman@intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Inline KASAN on x86 does tag mismatch reports by passing the faulty address and metadata through the INT3 instruction - scheme that's setup in the LLVM's compiler code (specifically HWAddressSanitizer.cpp). Add a kasan hook to the INT3 handling function. Disable KASAN in an INT3 core kernel selftest function since it can raise a false tag mismatch report and potentially panic the kernel. Make part of that hook - which decides whether to die or recover from a tag mismatch - arch independent to avoid duplicating a long comment on both x86 and arm64 architectures. Signed-off-by: Maciej Wieczor-Retman --- Changelog v5: - Add die to argument list of kasan_inline_recover() in arch/arm64/kernel/traps.c. Changelog v4: - Make kasan_handler() a stub in a header file. Remove #ifdef from traps.c. - Consolidate the "recover" comment into one place. - Make small changes to the patch message. MAINTAINERS | 2 +- arch/x86/include/asm/kasan.h | 26 ++++++++++++++++++++++++++ arch/x86/kernel/alternative.c | 4 +++- arch/x86/kernel/traps.c | 4 ++++ arch/x86/mm/Makefile | 2 ++ arch/x86/mm/kasan_inline.c | 23 +++++++++++++++++++++++ include/linux/kasan.h | 24 ++++++++++++++++++++++++ 7 files changed, 83 insertions(+), 2 deletions(-) create mode 100644 arch/x86/mm/kasan_inline.c diff --git a/MAINTAINERS b/MAINTAINERS index 788532771832..f5b1ce242002 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -13177,7 +13177,7 @@ S: Maintained B: https://bugzilla.kernel.org/buglist.cgi?component=3DSanitizers&product= =3DMemory%20Management F: Documentation/dev-tools/kasan.rst F: arch/*/include/asm/*kasan*.h -F: arch/*/mm/kasan_init* +F: arch/*/mm/kasan_* F: include/linux/kasan*.h F: lib/Kconfig.kasan F: mm/kasan/ diff --git a/arch/x86/include/asm/kasan.h b/arch/x86/include/asm/kasan.h index 1963eb2fcff3..5bf38bb836e1 100644 --- a/arch/x86/include/asm/kasan.h +++ b/arch/x86/include/asm/kasan.h @@ -6,7 +6,28 @@ #include #include #define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL) +#ifdef CONFIG_KASAN_SW_TAGS + +/* + * LLVM ABI for reporting tag mismatches in inline KASAN mode. + * On x86 the INT3 instruction is used to carry metadata in RAX + * to the KASAN report. + * + * SIZE refers to how many bytes the faulty memory access + * requested. + * WRITE bit, when set, indicates the access was a write, otherwise + * it was a read. + * RECOVER bit, when set, should allow the kernel to carry on after + * a tag mismatch. Otherwise die() is called. + */ +#define KASAN_RAX_RECOVER 0x20 +#define KASAN_RAX_WRITE 0x10 +#define KASAN_RAX_SIZE_MASK 0x0f +#define KASAN_RAX_SIZE(rax) (1 << ((rax) & KASAN_RAX_SIZE_MASK)) + +#else #define KASAN_SHADOW_SCALE_SHIFT 3 +#endif =20 /* * Compiler uses shadow offset assuming that addresses start @@ -35,10 +56,15 @@ #define __tag_shifted(tag) FIELD_PREP(GENMASK_ULL(60, 57), tag) #define __tag_reset(addr) (sign_extend64((u64)(addr), 56)) #define __tag_get(addr) ((u8)FIELD_GET(GENMASK_ULL(60, 57), (u64)addr)) +bool kasan_inline_handler(struct pt_regs *regs); #else #define __tag_shifted(tag) 0UL #define __tag_reset(addr) (addr) #define __tag_get(addr) 0 +static inline bool kasan_inline_handler(struct pt_regs *regs) +{ + return false; +} #endif /* CONFIG_KASAN_SW_TAGS */ =20 static inline void *__tag_set(const void *__addr, u8 tag) diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 2a330566e62b..4cb085daad31 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -2228,7 +2228,7 @@ int3_exception_notify(struct notifier_block *self, un= signed long val, void *data } =20 /* Must be noinline to ensure uniqueness of int3_selftest_ip. */ -static noinline void __init int3_selftest(void) +static noinline __no_sanitize_address void __init int3_selftest(void) { static __initdata struct notifier_block int3_exception_nb =3D { .notifier_call =3D int3_exception_notify, @@ -2236,6 +2236,7 @@ static noinline void __init int3_selftest(void) }; unsigned int val =3D 0; =20 + kasan_disable_current(); BUG_ON(register_die_notifier(&int3_exception_nb)); =20 /* @@ -2253,6 +2254,7 @@ static noinline void __init int3_selftest(void) =20 BUG_ON(val !=3D 1); =20 + kasan_enable_current(); unregister_die_notifier(&int3_exception_nb); } =20 diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 0f6f187b1a9e..2a119279980f 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -912,6 +912,10 @@ static bool do_int3(struct pt_regs *regs) if (kprobe_int3_handler(regs)) return true; #endif + + if (kasan_inline_handler(regs)) + return true; + res =3D notify_die(DIE_INT3, "int3", regs, 0, X86_TRAP_BP, SIGTRAP); =20 return res =3D=3D NOTIFY_STOP; diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile index 5b9908f13dcf..1dc18090cbe7 100644 --- a/arch/x86/mm/Makefile +++ b/arch/x86/mm/Makefile @@ -36,7 +36,9 @@ obj-$(CONFIG_PTDUMP) +=3D dump_pagetables.o obj-$(CONFIG_PTDUMP_DEBUGFS) +=3D debug_pagetables.o =20 KASAN_SANITIZE_kasan_init_$(BITS).o :=3D n +KASAN_SANITIZE_kasan_inline.o :=3D n obj-$(CONFIG_KASAN) +=3D kasan_init_$(BITS).o +obj-$(CONFIG_KASAN_SW_TAGS) +=3D kasan_inline.o =20 KMSAN_SANITIZE_kmsan_shadow.o :=3D n obj-$(CONFIG_KMSAN) +=3D kmsan_shadow.o diff --git a/arch/x86/mm/kasan_inline.c b/arch/x86/mm/kasan_inline.c new file mode 100644 index 000000000000..9f85dfd1c38b --- /dev/null +++ b/arch/x86/mm/kasan_inline.c @@ -0,0 +1,23 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include + +bool kasan_inline_handler(struct pt_regs *regs) +{ + int metadata =3D regs->ax; + u64 addr =3D regs->di; + u64 pc =3D regs->ip; + bool recover =3D metadata & KASAN_RAX_RECOVER; + bool write =3D metadata & KASAN_RAX_WRITE; + size_t size =3D KASAN_RAX_SIZE(metadata); + + if (user_mode(regs)) + return false; + + if (!kasan_report((void *)addr, size, write, pc)) + return false; + + kasan_inline_recover(recover, "Oops - KASAN", regs, metadata, die); + + return true; +} diff --git a/include/linux/kasan.h b/include/linux/kasan.h index 54481f8c30c5..8691ad870f3b 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -663,4 +663,28 @@ void kasan_non_canonical_hook(unsigned long addr); static inline void kasan_non_canonical_hook(unsigned long addr) { } #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */ =20 +#ifdef CONFIG_KASAN_SW_TAGS +/* + * The instrumentation allows to control whether we can proceed after + * a crash was detected. 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d="scan'208";a="169780844" Received: from bergbenj-mobl1.ger.corp.intel.com (HELO wieczorr-mobl1.intel.com) ([10.245.245.6]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:30:07 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 14/19] arm64: Unify software tag-based KASAN inline recovery path Date: Mon, 25 Aug 2025 22:24:39 +0200 Message-ID: X-Mailer: git-send-email 2.50.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" To avoid having a copy of a long comment explaining the intricacies of the inline KASAN recovery system and issues for every architecture that uses the software tag-based mode, a unified kasan_inline_recover() function was added. Use kasan_inline_recover() in the kasan brk handler to cleanup the long comment, that's kept in the non-arch KASAN code. Signed-off-by: Maciej Wieczor-Retman Acked-by: Catalin Marinas --- Changelog v5: - Split arm64 portion of patch 13/18 into this one. (Peter Zijlstra) arch/arm64/kernel/traps.c | 17 +---------------- 1 file changed, 1 insertion(+), 16 deletions(-) diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index f528b6041f6a..fe3c0104fe31 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -1068,22 +1068,7 @@ int kasan_brk_handler(struct pt_regs *regs, unsigned= long esr) =20 kasan_report(addr, size, write, pc); =20 - /* - * The instrumentation allows to control whether we can proceed after - * a crash was detected. This is done by passing the -recover flag to - * the compiler. Disabling recovery allows to generate more compact - * code. - * - * Unfortunately disabling recovery doesn't work for the kernel right - * now. KASAN reporting is disabled in some contexts (for example when - * the allocator accesses slab object metadata; this is controlled by - * current->kasan_depth). 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d="scan'208";a="169780899" Received: from bergbenj-mobl1.ger.corp.intel.com (HELO wieczorr-mobl1.intel.com) ([10.245.245.6]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:30:27 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 15/19] kasan: x86: Apply multishot to the inline report handler Date: Mon, 25 Aug 2025 22:24:40 +0200 Message-ID: <2f8115faaca5f79062542f930320cbfc6981863d.1756151769.git.maciej.wieczor-retman@intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" KASAN by default reports only one tag mismatch and based on other command line parameters either keeps going or panics. The multishot mechanism - enabled either through a command line parameter or by inline enable/disable function calls - lifts that restriction and allows an infinite number of tag mismatch reports to be shown. Inline KASAN uses the INT3 instruction to pass metadata to the report handling function. Currently the "recover" field in that metadata is broken in the compiler layer and causes every inline tag mismatch to panic the kernel. Check the multishot state in the KASAN hook called inside the INT3 handling function. Signed-off-by: Maciej Wieczor-Retman --- Changelog v4: - Add this patch to the series. arch/x86/mm/kasan_inline.c | 3 +++ include/linux/kasan.h | 3 +++ mm/kasan/report.c | 8 +++++++- 3 files changed, 13 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/kasan_inline.c b/arch/x86/mm/kasan_inline.c index 9f85dfd1c38b..f837caf32e6c 100644 --- a/arch/x86/mm/kasan_inline.c +++ b/arch/x86/mm/kasan_inline.c @@ -17,6 +17,9 @@ bool kasan_inline_handler(struct pt_regs *regs) if (!kasan_report((void *)addr, size, write, pc)) return false; =20 + if (kasan_multi_shot_enabled()) + return true; + kasan_inline_recover(recover, "Oops - KASAN", regs, metadata, die); =20 return true; diff --git a/include/linux/kasan.h b/include/linux/kasan.h index 8691ad870f3b..7a2527794549 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -663,7 +663,10 @@ void kasan_non_canonical_hook(unsigned long addr); static inline void kasan_non_canonical_hook(unsigned long addr) { } #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */ =20 +bool kasan_multi_shot_enabled(void); + #ifdef CONFIG_KASAN_SW_TAGS + /* * The instrumentation allows to control whether we can proceed after * a crash was detected. This is done by passing the -recover flag to diff --git a/mm/kasan/report.c b/mm/kasan/report.c index 50d487a0687a..9e830639e1b2 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c @@ -121,6 +121,12 @@ static void report_suppress_stop(void) #endif } =20 +bool kasan_multi_shot_enabled(void) +{ + return test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); +} +EXPORT_SYMBOL(kasan_multi_shot_enabled); + /* * Used to avoid reporting more than one KASAN bug unless kasan_multi_shot * is enabled. 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d="scan'208";a="169780957" Received: from bergbenj-mobl1.ger.corp.intel.com (HELO wieczorr-mobl1.intel.com) ([10.245.245.6]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:30:49 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 16/19] kasan: x86: Logical bit shift for kasan_mem_to_shadow Date: Mon, 25 Aug 2025 22:24:41 +0200 Message-ID: <169510f5490cba60916b144398543a489c31e2c1.1756151769.git.maciej.wieczor-retman@intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" While generally tag-based KASAN adopts an arithemitc bit shift to convert a memory address to a shadow memory address, it doesn't work for all cases on x86. Testing different shadow memory offsets proved that either 4 or 5 level paging didn't work correctly or inline mode ran into issues. Thus the best working scheme is the logical bit shift and non-canonical shadow offset that x86 uses for generic KASAN, of course adjusted for the increased granularity from 8 to 16 bytes. Add an arch specific implementation of kasan_mem_to_shadow() that uses the logical bit shift. The non-canonical hook tries to calculate whether an address came from kasan_mem_to_shadow(). First it checks whether this address fits into the legal set of values possible to output from the mem to shadow function. Tie both generic and tag-based x86 KASAN modes to the address range check associated with generic KASAN. Signed-off-by: Maciej Wieczor-Retman --- Changelog v4: - Add this patch to the series. arch/x86/include/asm/kasan.h | 8 ++++++++ mm/kasan/report.c | 5 +++-- 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/kasan.h b/arch/x86/include/asm/kasan.h index 5bf38bb836e1..f3e34a9754d2 100644 --- a/arch/x86/include/asm/kasan.h +++ b/arch/x86/include/asm/kasan.h @@ -53,6 +53,14 @@ =20 #ifdef CONFIG_KASAN_SW_TAGS =20 +static inline void *__kasan_mem_to_shadow(const void *addr) +{ + return (void *)((unsigned long)addr >> KASAN_SHADOW_SCALE_SHIFT) + + KASAN_SHADOW_OFFSET; +} + +#define kasan_mem_to_shadow(addr) __kasan_mem_to_shadow(addr) + #define __tag_shifted(tag) FIELD_PREP(GENMASK_ULL(60, 57), tag) #define __tag_reset(addr) (sign_extend64((u64)(addr), 56)) #define __tag_get(addr) ((u8)FIELD_GET(GENMASK_ULL(60, 57), (u64)addr)) diff --git a/mm/kasan/report.c b/mm/kasan/report.c index 9e830639e1b2..ee440ed1ecd3 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c @@ -648,13 +648,14 @@ void kasan_non_canonical_hook(unsigned long addr) const char *bug_type; =20 /* - * For Generic KASAN, kasan_mem_to_shadow() uses the logical right shift + * For Generic KASAN and Software Tag-Based mode on the x86 + * architecture, kasan_mem_to_shadow() uses the logical right shift * and never overflows with the chosen KASAN_SHADOW_OFFSET values (on * both x86 and arm64). 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d="scan'208";a="169780999" Received: from bergbenj-mobl1.ger.corp.intel.com (HELO wieczorr-mobl1.intel.com) ([10.245.245.6]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:31:11 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 17/19] mm: Unpoison pcpu chunks with base address tag Date: Mon, 25 Aug 2025 22:24:42 +0200 Message-ID: X-Mailer: git-send-email 2.50.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The problem presented here is related to NUMA systems and tag-based KASAN mode. It can be explained in the following points: 1. There can be more than one virtual memory chunk. 2. Chunk's base address has a tag. 3. The base address points at the first chunk and thus inherits the tag of the first chunk. 4. The subsequent chunks will be accessed with the tag from the first chunk. 5. Thus, the subsequent chunks need to have their tag set to match that of the first chunk. Refactor code by moving it into a helper in preparation for the actual fix. Signed-off-by: Maciej Wieczor-Retman Tested-by: Baoquan He --- Changelog v4: - Redo the patch message numbered list. - Do the refactoring in this patch and move additions to the next new one. Changelog v3: - Remove last version of this patch that just resets the tag on base_addr and add this patch that unpoisons all areas with the same tag instead. include/linux/kasan.h | 10 ++++++++++ mm/kasan/hw_tags.c | 11 +++++++++++ mm/kasan/shadow.c | 10 ++++++++++ mm/vmalloc.c | 4 +--- 4 files changed, 32 insertions(+), 3 deletions(-) diff --git a/include/linux/kasan.h b/include/linux/kasan.h index 7a2527794549..3ec432d7df9a 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -613,6 +613,13 @@ static __always_inline void kasan_poison_vmalloc(const= void *start, __kasan_poison_vmalloc(start, size); } =20 +void __kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms); +static __always_inline void kasan_unpoison_vmap_areas(struct vm_struct **v= ms, int nr_vms) +{ + if (kasan_enabled()) + __kasan_unpoison_vmap_areas(vms, nr_vms); +} + #else /* CONFIG_KASAN_VMALLOC */ =20 static inline void kasan_populate_early_vm_area_shadow(void *start, @@ -637,6 +644,9 @@ static inline void *kasan_unpoison_vmalloc(const void *= start, static inline void kasan_poison_vmalloc(const void *start, unsigned long s= ize) { } =20 +static inline void kasan_unpoison_vmap_areas(struct vm_struct **vms, int n= r_vms) +{ } + #endif /* CONFIG_KASAN_VMALLOC */ =20 #if (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) && \ diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c index 9a6927394b54..1f569df313c3 100644 --- a/mm/kasan/hw_tags.c +++ b/mm/kasan/hw_tags.c @@ -382,6 +382,17 @@ void __kasan_poison_vmalloc(const void *start, unsigne= d long size) */ } =20 +void __kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms) +{ + int area; + + for (area =3D 0 ; area < nr_vms ; area++) { + vms[area]->addr =3D __kasan_unpoison_vmalloc( + vms[area]->addr, vms[area]->size, + KASAN_VMALLOC_PROT_NORMAL); + } +} + #endif =20 void kasan_enable_hw_tags(void) diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c index d2c70cd2afb1..b41f74d68916 100644 --- a/mm/kasan/shadow.c +++ b/mm/kasan/shadow.c @@ -646,6 +646,16 @@ void __kasan_poison_vmalloc(const void *start, unsigne= d long size) kasan_poison(start, size, KASAN_VMALLOC_INVALID, false); } =20 +void __kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms) +{ + int area; + + for (area =3D 0 ; area < nr_vms ; area++) { + kasan_poison(vms[area]->addr, vms[area]->size, + arch_kasan_get_tag(vms[area]->addr), false); + } +} + #else /* CONFIG_KASAN_VMALLOC */ =20 int kasan_alloc_module_shadow(void *addr, size_t size, gfp_t gfp_mask) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index c93893fb8dd4..00be0abcaf60 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -4847,9 +4847,7 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned l= ong *offsets, * With hardware tag-based KASAN, marking is skipped for * non-VM_ALLOC mappings, see __kasan_unpoison_vmalloc(). */ - for (area =3D 0; 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25 Aug 2025 13:31:30 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 18/19] mm: Unpoison vms[area] addresses with a common tag Date: Mon, 25 Aug 2025 22:24:43 +0200 Message-ID: <3339d11e69c9127108fe8ef80a069b7b3bb07175.1756151769.git.maciej.wieczor-retman@intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The problem presented here is related to NUMA systems and tag-based KASAN mode. It can be explained in the following points: 1. There can be more than one virtual memory chunk. 2. Chunk's base address has a tag. 3. The base address points at the first chunk and thus inherits the tag of the first chunk. 4. The subsequent chunks will be accessed with the tag from the first chunk. 5. Thus, the subsequent chunks need to have their tag set to match that of the first chunk. Unpoison all vms[]->addr memory and pointers with the same tag to resolve the mismatch. Signed-off-by: Maciej Wieczor-Retman --- Changelog v4: - Move tagging the vms[]->addr to this new patch and leave refactoring there. - Comment the fix to provide some context. mm/kasan/shadow.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c index b41f74d68916..ee2488371784 100644 --- a/mm/kasan/shadow.c +++ b/mm/kasan/shadow.c @@ -646,13 +646,21 @@ void __kasan_poison_vmalloc(const void *start, unsign= ed long size) kasan_poison(start, size, KASAN_VMALLOC_INVALID, false); } =20 +/* + * A tag mismatch happens when calculating per-cpu chunk addresses, because + * they all inherit the tag from vms[0]->addr, even when nr_vms is bigger + * than 1. This is a problem because all the vms[]->addr come from separate + * allocations and have different tags so while the calculated address is + * correct the tag isn't. + */ void __kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms) { int area; =20 for (area =3D 0 ; area < nr_vms ; area++) { kasan_poison(vms[area]->addr, vms[area]->size, - arch_kasan_get_tag(vms[area]->addr), false); + arch_kasan_get_tag(vms[0]->addr), false); + arch_kasan_set_tag(vms[area]->addr, arch_kasan_get_tag(vms[0]->addr)); } } =20 --=20 2.50.1 From nobody Fri Oct 3 20:23:07 2025 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 206F81F419B; Mon, 25 Aug 2025 20:32:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.11 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; 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25 Aug 2025 13:32:14 -0700 X-CSE-ConnectionGUID: cXWZ7dRGQvecpjyhpKanvw== X-CSE-MsgGUID: bpDPHCHLRsKzMlSFZem02A== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="169781042" Received: from bergbenj-mobl1.ger.corp.intel.com (HELO wieczorr-mobl1.intel.com) ([10.245.245.6]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:31:53 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 19/19] x86: Make software tag-based kasan available Date: Mon, 25 Aug 2025 22:24:44 +0200 Message-ID: <3db48135aec987c99e8e6601249d4a4c023703c4.1756151769.git.maciej.wieczor-retman@intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Make CONFIG_KASAN_SW_TAGS available for x86 machines if they have ADDRESS_MASKING enabled (LAM) as that works similarly to Top-Byte Ignore (TBI) that allows the software tag-based mode on arm64 platform. Set scale macro based on KASAN mode: in software tag-based mode 16 bytes of memory map to one shadow byte and 8 in generic mode. Disable CONFIG_KASAN_INLINE and CONFIG_KASAN_STACK when CONFIG_KASAN_SW_TAGS is enabled on x86 until the appropriate compiler support is available. Signed-off-by: Maciej Wieczor-Retman --- Changelog v4: - Add x86 specific kasan_mem_to_shadow(). - Revert x86 to the older unsigned KASAN_SHADOW_OFFSET. Do the same to KASAN_SHADOW_START/END. - Modify scripts/gdb/linux/kasan.py to keep x86 using unsigned offset. - Disable inline and stack support when software tags are enabled on x86. Changelog v3: - Remove runtime_const from previous patch and merge the rest here. - Move scale shift definition back to header file. - Add new kasan offset for software tag based mode. - Fix patch message typo 32 -> 16, and 16 -> 8. - Update lib/Kconfig.kasan with x86 now having software tag-based support. Changelog v2: - Remove KASAN dense code. Documentation/arch/x86/x86_64/mm.rst | 6 ++++-- arch/x86/Kconfig | 4 +++- arch/x86/boot/compressed/misc.h | 1 + arch/x86/include/asm/kasan.h | 1 + arch/x86/kernel/setup.c | 2 ++ lib/Kconfig.kasan | 3 ++- scripts/gdb/linux/kasan.py | 4 ++-- 7 files changed, 15 insertions(+), 6 deletions(-) diff --git a/Documentation/arch/x86/x86_64/mm.rst b/Documentation/arch/x86/= x86_64/mm.rst index a6cf05d51bd8..ccbdbb4cda36 100644 --- a/Documentation/arch/x86/x86_64/mm.rst +++ b/Documentation/arch/x86/x86_64/mm.rst @@ -60,7 +60,8 @@ Complete virtual memory map with 4-level page tables ffffe90000000000 | -23 TB | ffffe9ffffffffff | 1 TB | ... unused= hole ffffea0000000000 | -22 TB | ffffeaffffffffff | 1 TB | virtual me= mory map (vmemmap_base) ffffeb0000000000 | -21 TB | ffffebffffffffff | 1 TB | ... unused= hole - ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN shad= ow memory + ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN shad= ow memory (generic mode) + fffff40000000000 | -8 TB | fffffbffffffffff | 8 TB | KASAN shad= ow memory (software tag-based mode) __________________|____________|__________________|_________|___________= _________________________________________________ | | Identical = layout to the 56-bit one from here on: @@ -130,7 +131,8 @@ Complete virtual memory map with 5-level page tables ffd2000000000000 | -11.5 PB | ffd3ffffffffffff | 0.5 PB | ... unused= hole ffd4000000000000 | -11 PB | ffd5ffffffffffff | 0.5 PB | virtual me= mory map (vmemmap_base) ffd6000000000000 | -10.5 PB | ffdeffffffffffff | 2.25 PB | ... unused= hole - ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN shad= ow memory + ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN shad= ow memory (generic mode) + ffeffc0000000000 | -6 PB | fffffbffffffffff | 4 PB | KASAN shad= ow memory (software tag-based mode) __________________|____________|__________________|_________|___________= _________________________________________________ | | Identical = layout to the 47-bit one from here on: diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index b8df57ac0f28..f44fec1190b6 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -69,6 +69,7 @@ config X86 select ARCH_CLOCKSOURCE_INIT select ARCH_CONFIGURES_CPU_MITIGATIONS select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE + select ARCH_DISABLE_KASAN_INLINE if X86_64 && KASAN_SW_TAGS select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRAT= ION select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64 select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG @@ -199,6 +200,7 @@ config X86 select HAVE_ARCH_JUMP_LABEL_RELATIVE select HAVE_ARCH_KASAN if X86_64 select HAVE_ARCH_KASAN_VMALLOC if X86_64 + select HAVE_ARCH_KASAN_SW_TAGS if ADDRESS_MASKING select HAVE_ARCH_KFENCE select HAVE_ARCH_KMSAN if X86_64 select HAVE_ARCH_KGDB @@ -403,7 +405,7 @@ config AUDIT_ARCH =20 config KASAN_SHADOW_OFFSET hex - depends on KASAN + default 0xeffffc0000000000 if KASAN_SW_TAGS default 0xdffffc0000000000 =20 config HAVE_INTEL_TXT diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/mis= c.h index db1048621ea2..ded92b439ada 100644 --- a/arch/x86/boot/compressed/misc.h +++ b/arch/x86/boot/compressed/misc.h @@ -13,6 +13,7 @@ #undef CONFIG_PARAVIRT_SPINLOCKS #undef CONFIG_KASAN #undef CONFIG_KASAN_GENERIC +#undef CONFIG_KASAN_SW_TAGS =20 #define __NO_FORTIFY =20 diff --git a/arch/x86/include/asm/kasan.h b/arch/x86/include/asm/kasan.h index f3e34a9754d2..385f4e9daab3 100644 --- a/arch/x86/include/asm/kasan.h +++ b/arch/x86/include/asm/kasan.h @@ -7,6 +7,7 @@ #include #define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL) #ifdef CONFIG_KASAN_SW_TAGS +#define KASAN_SHADOW_SCALE_SHIFT 4 =20 /* * LLVM ABI for reporting tag mismatches in inline KASAN mode. diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 1b2edd07a3e1..5b819f84f6db 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -1207,6 +1207,8 @@ void __init setup_arch(char **cmdline_p) =20 kasan_init(); =20 + kasan_init_sw_tags(); + /* * Sync back kernel address range. * diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan index f82889a830fa..9ddbc6aeb5d5 100644 --- a/lib/Kconfig.kasan +++ b/lib/Kconfig.kasan @@ -100,7 +100,8 @@ config KASAN_SW_TAGS =20 Requires GCC 11+ or Clang. =20 - Supported only on arm64 CPUs and relies on Top Byte Ignore. + Supported on arm64 CPUs that support Top Byte Ignore and on x86 CPUs + that support Linear Address Masking. =20 Consumes about 1/16th of available memory at kernel start and add an overhead of ~20% for dynamic allocations. diff --git a/scripts/gdb/linux/kasan.py b/scripts/gdb/linux/kasan.py index fca39968d308..4b86202b155f 100644 --- a/scripts/gdb/linux/kasan.py +++ b/scripts/gdb/linux/kasan.py @@ -7,7 +7,7 @@ # =20 import gdb -from linux import constants, mm +from linux import constants, utils, mm from ctypes import c_int64 as s64 =20 def help(): @@ -40,7 +40,7 @@ class KasanMemToShadow(gdb.Command): else: help() def kasan_mem_to_shadow(self, addr): - if constants.CONFIG_KASAN_SW_TAGS: + if constants.CONFIG_KASAN_SW_TAGS and not utils.is_target_arch('x8= 6'): addr =3D s64(addr) return (addr >> self.p_ops.KASAN_SHADOW_SCALE_SHIFT) + self.p_ops.= KASAN_SHADOW_OFFSET =20 --=20 2.50.1