From nobody Sun Feb 8 18:44:48 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 48551C6FD1F for ; Wed, 22 Mar 2023 17:05:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229747AbjCVRFn (ORCPT ); Wed, 22 Mar 2023 13:05:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59326 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231481AbjCVREt (ORCPT ); Wed, 22 Mar 2023 13:04:49 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E19032A14B; Wed, 22 Mar 2023 10:04:00 -0700 (PDT) Date: Wed, 22 Mar 2023 17:03:08 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1679504589; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=44nt7dVUV9OUctW6eaYTms76IFq36xY8mNNKTDTJ8gs=; b=i24Sep4G9uriDdYavjgiejso8gFeZRxtpE6dRPWg7WRDHQ8ZILFqGgBQSeTR/3M9NiHq+Y SQnqtfp3tMw7SMVSDqQ2q1iaH7rkDUeD/vWg+HAhYaI1cB3oTk183SlRY5iCaJUDBsFu/O HOl7EIAjGwrnujyh2U4JjGNLXYBJshqySQQZC3DB/9BxryYkIi/omOLH0QN5ZKiAUMzXCT Xkoe/BFNnSPXgqn+c+IA+qbm4Iqrj0dcYqK0DY8QO1qfSUbprSEjcqiCtRQvPY49jWK6jJ lZzFHnBvfnGiziUlQB+27m9wtWzDsZqfniV8A550+olmU9H8SfyCsbvyaPAQwg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1679504589; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=44nt7dVUV9OUctW6eaYTms76IFq36xY8mNNKTDTJ8gs=; b=T5KIGlwZ/z0eLJbbfZPTjM4l+Cos8UOthqTqxNZkjueFOctA0C66NZbGH4ycts4GUM1JG8 bNOxpl5584N6eUDw== From: "tip-bot2 for Kirill A. Shutemov" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/mm] x86/mm: Rework address range check in get_user() and put_user() Cc: Linus Torvalds , "Kirill A. Shutemov" , Dave Hansen , "Peter Zijlstra (Intel)" , x86@kernel.org, linux-kernel@vger.kernel.org MIME-Version: 1.0 Message-ID: <167950458889.5837.5617910719902761467.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the x86/mm branch of tip: Commit-ID: b19b74bc99b1501a550f4448d04d59b946dc617a Gitweb: https://git.kernel.org/tip/b19b74bc99b1501a550f4448d04d59b94= 6dc617a Author: Kirill A. Shutemov AuthorDate: Sun, 12 Mar 2023 14:25:56 +03:00 Committer: Dave Hansen CommitterDate: Thu, 16 Mar 2023 13:08:38 -07:00 x86/mm: Rework address range check in get_user() and put_user() The functions get_user() and put_user() check that the target address range resides in the user space portion of the virtual address space. In order to perform this check, the functions compare the end of the range against TASK_SIZE_MAX. For kernels compiled with CONFIG_X86_5LEVEL, this process requires some additional trickery using ALTERNATIVE, as TASK_SIZE_MAX depends on the paging mode in use. Linus suggested that this check could be simplified for 64-bit kernels. It is sufficient to check bit 63 of the address to ensure that the range belongs to user space. Additionally, the use of branches can be avoided by setting the target address to all ones if bit 63 is set. There's no need to check the end of the access range as there's huge gap between end of userspace range and start of the kernel range. The gap consists of canonical hole and unused ranges on both kernel and userspace sides. If an address with bit 63 set is passed down, it will trigger a #GP exception. _ASM_EXTABLE_UA() complains about this. Replace it with plain _ASM_EXTABLE() as it is expected behaviour now. The updated get_user() and put_user() checks are also compatible with Linear Address Masking, which allows user space to encode metadata in the upper bits of pointers and eliminates the need to untag the address before handling it. Suggested-by: Linus Torvalds Signed-off-by: Kirill A. Shutemov Signed-off-by: Dave Hansen Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/all/20230312112612.31869-2-kirill.shutemov%40= linux.intel.com --- arch/x86/lib/getuser.S | 83 +++++++++++++++-------------------------- arch/x86/lib/putuser.S | 54 ++++++++++++--------------- 2 files changed, 55 insertions(+), 82 deletions(-) diff --git a/arch/x86/lib/getuser.S b/arch/x86/lib/getuser.S index b70d98d..b64a2bd 100644 --- a/arch/x86/lib/getuser.S +++ b/arch/x86/lib/getuser.S @@ -37,22 +37,22 @@ =20 #define ASM_BARRIER_NOSPEC ALTERNATIVE "", "lfence", X86_FEATURE_LFENCE_RD= TSC =20 -#ifdef CONFIG_X86_5LEVEL -#define LOAD_TASK_SIZE_MINUS_N(n) \ - ALTERNATIVE __stringify(mov $((1 << 47) - 4096 - (n)),%rdx), \ - __stringify(mov $((1 << 56) - 4096 - (n)),%rdx), X86_FEATURE_LA57 -#else -#define LOAD_TASK_SIZE_MINUS_N(n) \ - mov $(TASK_SIZE_MAX - (n)),%_ASM_DX -#endif +.macro check_range size:req +.if IS_ENABLED(CONFIG_X86_64) + mov %rax, %rdx + sar $63, %rdx + or %rdx, %rax +.else + cmp $TASK_SIZE_MAX-\size+1, %eax + jae .Lbad_get_user + sbb %edx, %edx /* array_index_mask_nospec() */ + and %edx, %eax +.endif +.endm =20 .text SYM_FUNC_START(__get_user_1) - LOAD_TASK_SIZE_MINUS_N(0) - cmp %_ASM_DX,%_ASM_AX - jae bad_get_user - sbb %_ASM_DX, %_ASM_DX /* array_index_mask_nospec() */ - and %_ASM_DX, %_ASM_AX + check_range size=3D1 ASM_STAC 1: movzbl (%_ASM_AX),%edx xor %eax,%eax @@ -62,11 +62,7 @@ SYM_FUNC_END(__get_user_1) EXPORT_SYMBOL(__get_user_1) =20 SYM_FUNC_START(__get_user_2) - LOAD_TASK_SIZE_MINUS_N(1) - cmp %_ASM_DX,%_ASM_AX - jae bad_get_user - sbb %_ASM_DX, %_ASM_DX /* array_index_mask_nospec() */ - and %_ASM_DX, %_ASM_AX + check_range size=3D2 ASM_STAC 2: movzwl (%_ASM_AX),%edx xor %eax,%eax @@ -76,11 +72,7 @@ SYM_FUNC_END(__get_user_2) EXPORT_SYMBOL(__get_user_2) =20 SYM_FUNC_START(__get_user_4) - LOAD_TASK_SIZE_MINUS_N(3) - cmp %_ASM_DX,%_ASM_AX - jae bad_get_user - sbb %_ASM_DX, %_ASM_DX /* array_index_mask_nospec() */ - and %_ASM_DX, %_ASM_AX + check_range size=3D4 ASM_STAC 3: movl (%_ASM_AX),%edx xor %eax,%eax @@ -90,30 +82,17 @@ SYM_FUNC_END(__get_user_4) EXPORT_SYMBOL(__get_user_4) =20 SYM_FUNC_START(__get_user_8) -#ifdef CONFIG_X86_64 - LOAD_TASK_SIZE_MINUS_N(7) - cmp %_ASM_DX,%_ASM_AX - jae bad_get_user - sbb %_ASM_DX, %_ASM_DX /* array_index_mask_nospec() */ - and %_ASM_DX, %_ASM_AX + check_range size=3D8 ASM_STAC +#ifdef CONFIG_X86_64 4: movq (%_ASM_AX),%rdx - xor %eax,%eax - ASM_CLAC - RET #else - LOAD_TASK_SIZE_MINUS_N(7) - cmp %_ASM_DX,%_ASM_AX - jae bad_get_user_8 - sbb %_ASM_DX, %_ASM_DX /* array_index_mask_nospec() */ - and %_ASM_DX, %_ASM_AX - ASM_STAC 4: movl (%_ASM_AX),%edx 5: movl 4(%_ASM_AX),%ecx +#endif xor %eax,%eax ASM_CLAC RET -#endif SYM_FUNC_END(__get_user_8) EXPORT_SYMBOL(__get_user_8) =20 @@ -166,7 +145,7 @@ EXPORT_SYMBOL(__get_user_nocheck_8) =20 SYM_CODE_START_LOCAL(.Lbad_get_user_clac) ASM_CLAC -bad_get_user: +.Lbad_get_user: xor %edx,%edx mov $(-EFAULT),%_ASM_AX RET @@ -184,23 +163,23 @@ SYM_CODE_END(.Lbad_get_user_8_clac) #endif =20 /* get_user */ - _ASM_EXTABLE_UA(1b, .Lbad_get_user_clac) - _ASM_EXTABLE_UA(2b, .Lbad_get_user_clac) - _ASM_EXTABLE_UA(3b, .Lbad_get_user_clac) + _ASM_EXTABLE(1b, .Lbad_get_user_clac) + _ASM_EXTABLE(2b, .Lbad_get_user_clac) + _ASM_EXTABLE(3b, .Lbad_get_user_clac) #ifdef CONFIG_X86_64 - _ASM_EXTABLE_UA(4b, .Lbad_get_user_clac) + _ASM_EXTABLE(4b, .Lbad_get_user_clac) #else - _ASM_EXTABLE_UA(4b, .Lbad_get_user_8_clac) - _ASM_EXTABLE_UA(5b, .Lbad_get_user_8_clac) + _ASM_EXTABLE(4b, .Lbad_get_user_8_clac) + _ASM_EXTABLE(5b, .Lbad_get_user_8_clac) #endif =20 /* __get_user */ - _ASM_EXTABLE_UA(6b, .Lbad_get_user_clac) - _ASM_EXTABLE_UA(7b, .Lbad_get_user_clac) - _ASM_EXTABLE_UA(8b, .Lbad_get_user_clac) + _ASM_EXTABLE(6b, .Lbad_get_user_clac) + _ASM_EXTABLE(7b, .Lbad_get_user_clac) + _ASM_EXTABLE(8b, .Lbad_get_user_clac) #ifdef CONFIG_X86_64 - _ASM_EXTABLE_UA(9b, .Lbad_get_user_clac) + _ASM_EXTABLE(9b, .Lbad_get_user_clac) #else - _ASM_EXTABLE_UA(9b, .Lbad_get_user_8_clac) - _ASM_EXTABLE_UA(10b, .Lbad_get_user_8_clac) + _ASM_EXTABLE(9b, .Lbad_get_user_8_clac) + _ASM_EXTABLE(10b, .Lbad_get_user_8_clac) #endif diff --git a/arch/x86/lib/putuser.S b/arch/x86/lib/putuser.S index 3212522..3062d09 100644 --- a/arch/x86/lib/putuser.S +++ b/arch/x86/lib/putuser.S @@ -33,20 +33,20 @@ * as they get called from within inline assembly. */ =20 -#ifdef CONFIG_X86_5LEVEL -#define LOAD_TASK_SIZE_MINUS_N(n) \ - ALTERNATIVE __stringify(mov $((1 << 47) - 4096 - (n)),%rbx), \ - __stringify(mov $((1 << 56) - 4096 - (n)),%rbx), X86_FEATURE_LA57 -#else -#define LOAD_TASK_SIZE_MINUS_N(n) \ - mov $(TASK_SIZE_MAX - (n)),%_ASM_BX -#endif +.macro check_range size:req +.if IS_ENABLED(CONFIG_X86_64) + mov %rcx, %rbx + sar $63, %rbx + or %rbx, %rcx +.else + cmp $TASK_SIZE_MAX-\size+1, %ecx + jae .Lbad_put_user +.endif +.endm =20 .text SYM_FUNC_START(__put_user_1) - LOAD_TASK_SIZE_MINUS_N(0) - cmp %_ASM_BX,%_ASM_CX - jae .Lbad_put_user + check_range size=3D1 ASM_STAC 1: movb %al,(%_ASM_CX) xor %ecx,%ecx @@ -66,9 +66,7 @@ SYM_FUNC_END(__put_user_nocheck_1) EXPORT_SYMBOL(__put_user_nocheck_1) =20 SYM_FUNC_START(__put_user_2) - LOAD_TASK_SIZE_MINUS_N(1) - cmp %_ASM_BX,%_ASM_CX - jae .Lbad_put_user + check_range size=3D2 ASM_STAC 3: movw %ax,(%_ASM_CX) xor %ecx,%ecx @@ -88,9 +86,7 @@ SYM_FUNC_END(__put_user_nocheck_2) EXPORT_SYMBOL(__put_user_nocheck_2) =20 SYM_FUNC_START(__put_user_4) - LOAD_TASK_SIZE_MINUS_N(3) - cmp %_ASM_BX,%_ASM_CX - jae .Lbad_put_user + check_range size=3D4 ASM_STAC 5: movl %eax,(%_ASM_CX) xor %ecx,%ecx @@ -110,9 +106,7 @@ SYM_FUNC_END(__put_user_nocheck_4) EXPORT_SYMBOL(__put_user_nocheck_4) =20 SYM_FUNC_START(__put_user_8) - LOAD_TASK_SIZE_MINUS_N(7) - cmp %_ASM_BX,%_ASM_CX - jae .Lbad_put_user + check_range size=3D8 ASM_STAC 7: mov %_ASM_AX,(%_ASM_CX) #ifdef CONFIG_X86_32 @@ -144,15 +138,15 @@ SYM_CODE_START_LOCAL(.Lbad_put_user_clac) RET SYM_CODE_END(.Lbad_put_user_clac) =20 - _ASM_EXTABLE_UA(1b, .Lbad_put_user_clac) - _ASM_EXTABLE_UA(2b, .Lbad_put_user_clac) - _ASM_EXTABLE_UA(3b, .Lbad_put_user_clac) - _ASM_EXTABLE_UA(4b, .Lbad_put_user_clac) - _ASM_EXTABLE_UA(5b, .Lbad_put_user_clac) - _ASM_EXTABLE_UA(6b, .Lbad_put_user_clac) - _ASM_EXTABLE_UA(7b, .Lbad_put_user_clac) - _ASM_EXTABLE_UA(9b, .Lbad_put_user_clac) + _ASM_EXTABLE(1b, .Lbad_put_user_clac) + _ASM_EXTABLE(2b, .Lbad_put_user_clac) + _ASM_EXTABLE(3b, .Lbad_put_user_clac) + _ASM_EXTABLE(4b, .Lbad_put_user_clac) + _ASM_EXTABLE(5b, .Lbad_put_user_clac) + _ASM_EXTABLE(6b, .Lbad_put_user_clac) + _ASM_EXTABLE(7b, .Lbad_put_user_clac) + _ASM_EXTABLE(9b, .Lbad_put_user_clac) #ifdef CONFIG_X86_32 - _ASM_EXTABLE_UA(8b, .Lbad_put_user_clac) - _ASM_EXTABLE_UA(10b, .Lbad_put_user_clac) + _ASM_EXTABLE(8b, .Lbad_put_user_clac) + _ASM_EXTABLE(10b, .Lbad_put_user_clac) #endif