From nobody Fri Apr 10 20:53:40 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 78F10C4332F for ; Tue, 27 Dec 2022 03:09:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230223AbiL0DJO (ORCPT ); Mon, 26 Dec 2022 22:09:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38222 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229767AbiL0DIw (ORCPT ); Mon, 26 Dec 2022 22:08:52 -0500 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B3201261C for ; Mon, 26 Dec 2022 19:08:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1672110530; x=1703646530; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=yO+iUKN0r9KVMUOqq6nIAT1LjszIJDhKiqjV1XdDapw=; b=P93IF+hn1r49BrfN7TffaFJdPRSeLGuBGI4X540L42IswYyzhjHoyMW7 gGD7XMp2E2VGhxZg0/+HjcONWtdnT8UMA4F/bKaxU7xlXQVLDX8SBxjNs ROwdQVmqgzMBLLrXwAL9sS+f1SDaMx0HGdpPqoLUI/0ypHYj+Q66JaF+a HDvOgF364lh5Uxr5QTBF/TTz04X7RX4Ex5tSPF6HL217RypFKZOcRMhfW QALRM4vKZ5ErsXgGs4LyGz3Elu5io2LxCk6tFpznggHvccnA8OZJ3oZsj GjGpGJiw59/cMtplushuKPmQnEKOoYsMG0rMHuscOmQvvUBALAxz/Aqyu A==; X-IronPort-AV: E=McAfee;i="6500,9779,10572"; a="300994688" X-IronPort-AV: E=Sophos;i="5.96,277,1665471600"; d="scan'208";a="300994688" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Dec 2022 19:08:50 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10572"; a="741605215" X-IronPort-AV: E=Sophos;i="5.96,277,1665471600"; d="scan'208";a="741605215" Received: from ppogotov-mobl.ger.corp.intel.com (HELO box.shutemov.name) ([10.252.62.152]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Dec 2022 19:08:45 -0800 Received: by box.shutemov.name (Postfix, from userid 1000) id ABB7210BBB2; Tue, 27 Dec 2022 06:08:36 +0300 (+03) From: "Kirill A. Shutemov" To: Dave Hansen , Andy Lutomirski , Peter Zijlstra Cc: x86@kernel.org, Kostya Serebryany , Andrey Ryabinin , Andrey Konovalov , Alexander Potapenko , Taras Madan , Dmitry Vyukov , "H . J . Lu" , Andi Kleen , Rick Edgecombe , Bharata B Rao , Jacob Pan , Ashok Raj , Linus Torvalds , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" Subject: [PATCHv13 05/16] x86/uaccess: Provide untagged_addr() and remove tags before address check Date: Tue, 27 Dec 2022 06:08:18 +0300 Message-Id: <20221227030829.12508-6-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.38.2 In-Reply-To: <20221227030829.12508-1-kirill.shutemov@linux.intel.com> References: <20221227030829.12508-1-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" untagged_addr() is a helper used by the core-mm to strip tag bits and get the address to the canonical shape. In only handles userspace addresses. The untagging mask is stored in mmu_context and will be set on enabling LAM for the process. The tags must not be included into check whether it's okay to access the userspace address. Strip tags in access_ok(). get_user() and put_user() don't use access_ok(), but check access against TASK_SIZE directly in assembly. Strip tags, before calling into the assembly helper. Signed-off-by: Kirill A. Shutemov Acked-by: Peter Zijlstra (Intel) Acked-by: Andy Lutomirski Tested-by: Alexander Potapenko --- arch/x86/include/asm/mmu.h | 3 ++ arch/x86/include/asm/mmu_context.h | 11 +++++++ arch/x86/include/asm/uaccess.h | 47 +++++++++++++++++++++++++++--- arch/x86/kernel/process.c | 3 ++ 4 files changed, 60 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h index 9a046aacad8d..ed72fcd2292d 100644 --- a/arch/x86/include/asm/mmu.h +++ b/arch/x86/include/asm/mmu.h @@ -43,6 +43,9 @@ typedef struct { =20 /* Active LAM mode: X86_CR3_LAM_U48 or X86_CR3_LAM_U57 or 0 (disabled) */ unsigned long lam_cr3_mask; + + /* Significant bits of the virtual address. Excludes tag bits. */ + u64 untag_mask; #endif =20 struct mutex lock; diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_= context.h index 464cca41d20a..71581cb4811b 100644 --- a/arch/x86/include/asm/mmu_context.h +++ b/arch/x86/include/asm/mmu_context.h @@ -100,6 +100,12 @@ static inline unsigned long mm_lam_cr3_mask(struct mm_= struct *mm) static inline void dup_lam(struct mm_struct *oldmm, struct mm_struct *mm) { mm->context.lam_cr3_mask =3D oldmm->context.lam_cr3_mask; + mm->context.untag_mask =3D oldmm->context.untag_mask; +} + +static inline void mm_reset_untag_mask(struct mm_struct *mm) +{ + mm->context.untag_mask =3D -1UL; } =20 #else @@ -112,6 +118,10 @@ static inline unsigned long mm_lam_cr3_mask(struct mm_= struct *mm) static inline void dup_lam(struct mm_struct *oldmm, struct mm_struct *mm) { } + +static inline void mm_reset_untag_mask(struct mm_struct *mm) +{ +} #endif =20 #define enter_lazy_tlb enter_lazy_tlb @@ -138,6 +148,7 @@ static inline int init_new_context(struct task_struct *= tsk, mm->context.execute_only_pkey =3D -1; } #endif + mm_reset_untag_mask(mm); init_new_context_ldt(mm); return 0; } diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 1cc756eafa44..cbb463e9344f 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -7,6 +7,7 @@ #include #include #include +#include #include #include #include @@ -21,6 +22,37 @@ static inline bool pagefault_disabled(void); # define WARN_ON_IN_IRQ() #endif =20 +#ifdef CONFIG_X86_64 +/* + * Mask out tag bits from the address. + * + * Magic with the 'sign' allows to untag userspace pointer without any bra= nches + * while leaving kernel addresses intact. + */ +#define __untagged_addr(mm, addr) ({ \ + u64 __addr =3D (__force u64)(addr); \ + s64 sign =3D (s64)__addr >> 63; \ + __addr &=3D READ_ONCE((mm)->context.untag_mask) | sign; \ + (__force __typeof__(addr))__addr; \ +}) + +#define untagged_addr(addr) __untagged_addr(current->mm, addr) + +#define untagged_addr_remote(mm, addr) ({ \ + mmap_assert_locked(mm); \ + __untagged_addr(mm, addr); \ +}) + +#define untagged_ptr(ptr) ({ \ + u64 __ptrval =3D (__force u64)(ptr); \ + __ptrval =3D untagged_addr(__ptrval); \ + (__force __typeof__(ptr))__ptrval; \ +}) +#else +#define untagged_addr(addr) (addr) +#define untagged_ptr(ptr) (ptr) +#endif + /** * access_ok - Checks if a user space pointer is valid * @addr: User space pointer to start of block to check @@ -38,10 +70,10 @@ static inline bool pagefault_disabled(void); * Return: true (nonzero) if the memory block may be valid, false (zero) * if it is definitely invalid. */ -#define access_ok(addr, size) \ +#define access_ok(addr, size) \ ({ \ WARN_ON_IN_IRQ(); \ - likely(__access_ok(addr, size)); \ + likely(__access_ok(untagged_addr(addr), size)); \ }) =20 #include @@ -127,7 +159,11 @@ extern int __get_user_bad(void); * Return: zero on success, or -EFAULT on error. * On error, the variable @x is set to zero. */ -#define get_user(x,ptr) ({ might_fault(); do_get_user_call(get_user,x,ptr)= ; }) +#define get_user(x,ptr) \ +({ \ + might_fault(); \ + do_get_user_call(get_user,x,untagged_ptr(ptr)); \ +}) =20 /** * __get_user - Get a simple variable from user space, with less checking. @@ -227,7 +263,10 @@ extern void __put_user_nocheck_8(void); * * Return: zero on success, or -EFAULT on error. */ -#define put_user(x, ptr) ({ might_fault(); do_put_user_call(put_user,x,ptr= ); }) +#define put_user(x, ptr) ({ \ + might_fault(); \ + do_put_user_call(put_user,x,untagged_ptr(ptr)); \ +}) =20 /** * __put_user - Write a simple value into user space, with less checking. diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 40d156a31676..ef6bde1d40d8 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -47,6 +47,7 @@ #include #include #include +#include =20 #include "process.h" =20 @@ -367,6 +368,8 @@ void arch_setup_new_exec(void) task_clear_spec_ssb_noexec(current); speculation_ctrl_update(read_thread_flags()); } + + mm_reset_untag_mask(current->mm); } =20 #ifdef CONFIG_X86_IOPL_IOPERM --=20 2.38.2