diff options
| author | Andy Lutomirski <luto@kernel.org> | 2019-02-22 17:17:04 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-03-05 17:58:03 +0100 |
| commit | 24e988f6fcae54009891c1bfdd4112fa5656af70 (patch) | |
| tree | abdf7588df3e5a1674bba0da4542624fa409a373 | |
| parent | e01f09149d2dc540c0ef1c0bec48c45cd592ec14 (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>
| -rw-r--r-- | arch/x86/include/asm/uaccess.h | 7 |
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); \ }) |