diff options
authorAndy Lutomirski <luto@kernel.org>2019-02-22 17:17:04 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-03-05 17:58:54 +0100
commit7371994d6cfa2f06f9c8a0818ed1eabcfc507ea0 (patch)
parent9f77e4cb12d4d98b08d8804e3712a4075a2bdd1d (diff)
x86/uaccess: Don't leak the AC flag into __put_user() value evaluation
commit 2a418cf3f5f1caf911af288e978d61c9844b0695 upstream. 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 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 4 insertions, 3 deletions
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index aae77eb8491c..4111edb3188e 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -293,8 +293,7 @@ do { \
__put_user_asm(x, ptr, retval, "l", "k", "ir", errret); \
break; \
case 8: \
- __put_user_asm_u64((__typeof__(*ptr))(x), ptr, retval, \
- errret); \
+ __put_user_asm_u64(x, ptr, retval, errret); \
break; \
default: \
__put_user_bad(); \
@@ -440,8 +439,10 @@ do { \
#define __put_user_nocheck(x, ptr, size) \
({ \
int __pu_err; \
+ __typeof__(*(ptr)) __pu_val; \
+ __pu_val = x; \
__uaccess_begin(); \
- __put_user_size((x), (ptr), (size), __pu_err, -EFAULT); \
+ __put_user_size(__pu_val, (ptr), (size), __pu_err, -EFAULT);\
__uaccess_end(); \
__builtin_expect(__pu_err, 0); \