From nobody Tue Apr 7 08:50:50 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 6C3D7C0502C for ; Tue, 30 Aug 2022 01:02:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229797AbiH3BCC (ORCPT ); Mon, 29 Aug 2022 21:02:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35734 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229655AbiH3BBi (ORCPT ); Mon, 29 Aug 2022 21:01:38 -0400 Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5B9EEA00D2 for ; Mon, 29 Aug 2022 18:01:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1661821297; x=1693357297; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=T/1SON8x3I6gBc9Gilj4Fh9sNy8RCIdk2WdRlZ6DEwk=; b=GuVeLcV4+tPgYeCQrtfLRlhK0IhOhSkdUdEgJX29GvPhvivoRxKavfM9 /6iAb0/tM/RVrP15a0cXpqwpvt6mIknTgM71wmXUcVSD+wzC7Xh82AqZe dQ8EJrvLNFJc8YXNXRS0dtnW6Bgq/UMTZJfU0B4+SiOuzBUa00QNyKiLg iFg2TQq3juFLr2Ci0vH4tLI/+3cNvz5DERiR4qXfWdcTaIhxMaKTLBlJh D84KqGRb4Su5uIY4ak9K+RrwfHt9bkZjYaHXtg2TZOtgMc/i8NvsyQK+O drqJd04N3/Z8xP2q0T9rbjX1X43TVJAxUMOGtm5GUwIrI4wSjKykmbR6+ A==; X-IronPort-AV: E=McAfee;i="6500,9779,10454"; a="278063008" X-IronPort-AV: E=Sophos;i="5.93,273,1654585200"; d="scan'208";a="278063008" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Aug 2022 18:01:37 -0700 X-IronPort-AV: E=Sophos;i="5.93,273,1654585200"; d="scan'208";a="939803136" Received: from fpalamon-mobl.amr.corp.intel.com (HELO box.shutemov.name) ([10.252.54.23]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Aug 2022 18:01:32 -0700 Received: by box.shutemov.name (Postfix, from userid 1000) id 8B9E1104167; Tue, 30 Aug 2022 04:01:24 +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 , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" Subject: [PATCHv8 05/11] x86/uaccess: Provide untagged_addr() and remove tags before address check Date: Tue, 30 Aug 2022 04:00:58 +0300 Message-Id: <20220830010104.1282-6-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220830010104.1282-1-kirill.shutemov@linux.intel.com> References: <20220830010104.1282-1-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 Tested-by: Alexander Potapenko Acked-by: Peter Zijlstra (Intel) --- arch/x86/include/asm/mmu.h | 3 +++ arch/x86/include/asm/mmu_context.h | 11 ++++++++ arch/x86/include/asm/uaccess.h | 42 +++++++++++++++++++++++++++--- arch/x86/kernel/process.c | 3 +++ 4 files changed, 56 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h index 002889ca8978..2fdb390040b5 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 69c943b2ae90..5bd3d46685dc 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 913e593a3b45..803241dfc473 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -6,6 +6,7 @@ */ #include #include +#include #include #include #include @@ -20,6 +21,30 @@ 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 (mm)->context.untag_mask | sign; \ + (__force __typeof__(addr))__addr; \ +}) + +#define untagged_ptr(mm, ptr) ({ \ + u64 __ptrval =3D (__force u64)(ptr); \ + __ptrval =3D untagged_addr(mm, __ptrval); \ + (__force __typeof__(*(ptr)) *)__ptrval; \ +}) +#else +#define untagged_addr(mm, addr) (addr) +#define untagged_ptr(mm, ptr) (ptr) +#endif + /** * access_ok - Checks if a user space pointer is valid * @addr: User space pointer to start of block to check @@ -40,7 +65,7 @@ static inline bool pagefault_disabled(void); #define access_ok(addr, size) \ ({ \ WARN_ON_IN_IRQ(); \ - likely(__access_ok(addr, size)); \ + likely(__access_ok(untagged_addr(current->mm, addr), size)); \ }) =20 #include @@ -125,7 +150,13 @@ 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) \ +({ \ + __typeof__(*(ptr)) __user *__ptr_clean; \ + __ptr_clean =3D untagged_ptr(current->mm, ptr); \ + might_fault(); \ + do_get_user_call(get_user,x,__ptr_clean); \ +}) =20 /** * __get_user - Get a simple variable from user space, with less checking. @@ -222,7 +253,12 @@ 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) ({ \ + __typeof__(*(ptr)) __user *__ptr_clean; \ + __ptr_clean =3D untagged_ptr(current->mm, ptr); \ + might_fault(); \ + do_put_user_call(put_user,x,__ptr_clean); \ +}) =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 58a6ea472db9..b0e86fb11ffa 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 2.35.1