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authorAndy Lutomirski <luto@kernel.org>2019-02-22 17:17:04 -0800
committerBorislav Petkov <bp@suse.de>2019-02-25 20:17:05 +0100
commit2a418cf3f5f1caf911af288e978d61c9844b0695 (patch)
tree328d5988460e15b341ba24c37fe048e7d1df34ce
parentf331e766c4be33f4338574f3c9f7f77e98ab4571 (diff)
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 and fixed up whitespace. ] 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> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.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
-rw-r--r--arch/x86/include/asm/uaccess.h6
1 files changed, 4 insertions, 2 deletions
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index a77445d1b034..28376aa2d053 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(); \