From: tip-bot for Andy Lutomirski <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: mingo@kernel.org, hpa@zytor.com, brgerst@gmail.com,
peterz@infradead.org, luto@kernel.org, dvlasenk@redhat.com,
linux-kernel@vger.kernel.org, bp@suse.de, tglx@linutronix.de,
jpoimboe@redhat.com, torvalds@linux-foundation.org
Subject: [tip:x86/urgent] x86/uaccess: Don't leak the AC flag into __put_user() value evaluation
Date: Mon, 25 Feb 2019 10:10:46 -0800 [thread overview]
Message-ID: <tip-1ee2bd5e09195d5476daefec5c64ba597a0a9920@git.kernel.org> (raw)
In-Reply-To: <20190225125231.845656645@infradead.org>
Commit-ID: 1ee2bd5e09195d5476daefec5c64ba597a0a9920
Gitweb: https://git.kernel.org/tip/1ee2bd5e09195d5476daefec5c64ba597a0a9920
Author: Andy Lutomirski <luto@kernel.org>
AuthorDate: Fri, 22 Feb 2019 17:17:04 -0800
Committer: Borislav Petkov <bp@suse.de>
CommitDate: Mon, 25 Feb 2019 18:55:04 +0100
x86/uaccess: Don't leak the AC flag into __put_user() value evaluation
When calling __put_user(foo(), ptr), the __put_user() macro would call
foo() in between __uaccess_begin() and __uaccess_end(). If that code
were buggy, then those bugs would be run without SMAP protection.
Fortunately, there seem to be few instances of the problem in the
kernel. Nevertheless, __put_user() should be fixed to avoid doing this.
Therefore, evaluate __put_user()'s argument before setting AC.
This issue was noticed when an objtool hack by Peter Zijlstra complained
about genregs_get() and I compared the assembly output to the C source.
[ bp: Massage commit message. ]
Fixes: 11f1a4b9755f ("x86: reorganize SMAP handling in user space accesses")
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20190225125231.845656645@infradead.org
---
arch/x86/include/asm/uaccess.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index a77445d1b034..d7688efacf29 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -284,7 +284,7 @@ do { \
__put_user_goto(x, ptr, "l", "k", "ir", label); \
break; \
case 8: \
- __put_user_goto_u64((__typeof__(*ptr))(x), ptr, label); \
+ __put_user_goto_u64(x, ptr, label); \
break; \
default: \
__put_user_bad(); \
@@ -431,8 +431,10 @@ do { \
({ \
__label__ __pu_label; \
int __pu_err = -EFAULT; \
+ __typeof__(*(ptr)) __pu_val; \
+ __pu_val = x; \
__uaccess_begin(); \
- __put_user_size((x), (ptr), (size), __pu_label); \
+ __put_user_size(__pu_val, (ptr), (size), __pu_label); \
__pu_err = 0; \
__pu_label: \
__uaccess_end(); \
next prev parent reply other threads:[~2019-02-25 18:11 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-25 12:43 [PATCH 0/6] objtool: UACCESS validation Peter Zijlstra
2019-02-25 12:43 ` [PATCH 1/6] x86/uaccess: Dont evaluate argument inside AC region Peter Zijlstra
2019-02-25 15:43 ` Andy Lutomirski
2019-02-25 16:02 ` Peter Zijlstra
2019-02-25 16:36 ` Borislav Petkov
2019-02-25 16:50 ` Andy Lutomirski
2019-02-25 19:09 ` Linus Torvalds
2019-02-25 19:18 ` Borislav Petkov
2019-02-25 18:10 ` tip-bot for Andy Lutomirski [this message]
2019-02-25 19:46 ` [tip:x86/urgent] x86/uaccess: Don't leak the AC flag into __put_user() value evaluation tip-bot for Andy Lutomirski
2019-02-25 12:43 ` [PATCH 2/6] x86/ia32: Fix ia32_restore_sigcontext AC leak Peter Zijlstra
2019-02-25 15:41 ` Andy Lutomirski
2019-02-25 16:10 ` Peter Zijlstra
2019-02-25 16:29 ` Andy Lutomirski
2019-02-25 16:37 ` Peter Zijlstra
2019-02-25 16:41 ` Peter Zijlstra
2019-02-25 16:49 ` Andy Lutomirski
2019-02-25 12:43 ` [PATCH 3/6] objtool: Set insn->func for alternatives Peter Zijlstra
2019-02-25 12:43 ` [PATCH 4/6] objtool: Replace STACK_FRAME_NON_STANDARD annotation Peter Zijlstra
2019-02-25 16:11 ` Josh Poimboeuf
2019-02-25 16:17 ` Peter Zijlstra
2019-02-25 16:23 ` Josh Poimboeuf
2019-02-27 12:20 ` Peter Zijlstra
2019-02-28 0:30 ` Andy Lutomirski
2019-02-25 12:43 ` [PATCH 5/6] objtool: Add UACCESS validation Peter Zijlstra
2019-02-25 15:53 ` Andy Lutomirski
2019-02-25 16:12 ` Peter Zijlstra
2019-02-25 17:15 ` Peter Zijlstra
2019-02-25 17:34 ` Linus Torvalds
2019-02-25 17:38 ` Josh Poimboeuf
2019-02-27 14:08 ` Peter Zijlstra
2019-02-27 14:17 ` Andrey Ryabinin
2019-02-27 14:26 ` Peter Zijlstra
2019-02-27 14:33 ` Peter Zijlstra
2019-02-27 15:40 ` Dmitry Vyukov
2019-02-27 17:28 ` Peter Zijlstra
2019-02-28 9:40 ` Peter Zijlstra
2019-02-28 9:59 ` Dmitry Vyukov
2019-02-28 10:05 ` Dmitry Vyukov
2019-02-28 10:52 ` Peter Zijlstra
2019-02-27 16:18 ` Linus Torvalds
2019-02-27 17:30 ` Peter Zijlstra
2019-02-27 17:36 ` Linus Torvalds
2019-02-25 12:43 ` [PATCH 6/6] objtool: Add Direction Flag validation Peter Zijlstra
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