diff options
| author | Andy Lutomirski <luto@kernel.org> | 2019-02-22 17:17:04 -0800 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2019-02-25 20:17:05 +0100 |
| commit | 2a418cf3f5f1caf911af288e978d61c9844b0695 (patch) | |
| tree | 328d5988460e15b341ba24c37fe048e7d1df34ce | |
| parent | f331e766c4be33f4338574f3c9f7f77e98ab4571 (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.h | 6 |
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(); \ |