3.16.74-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Peter Zijlstra <[email protected]> commit 6ae865615fc43d014da2fd1f1bba7e81ee622d1b upstream. The __put_user() macro evaluates it's @ptr argument inside the __uaccess_begin() / __uaccess_end() region. While this would normally not be expected to be an issue, an UBSAN bug (it ignored -fwrapv, fixed in GCC 8+) would transform the @ptr evaluation for: drivers/gpu/drm/i915/i915_gem_execbuffer.c: if (unlikely(__put_user(offset, &urelocs[r-stack].presumed_offset))) { into a signed-overflow-UB check and trigger the objtool AC validation. Finish this commit: 2a418cf3f5f1 ("x86/uaccess: Don't leak the AC flag into __put_user() value evaluation") and explicitly evaluate all 3 arguments early. Reported-by: Randy Dunlap <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Acked-by: Randy Dunlap <[email protected]> # build-tested Acked-by: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Fixes: 2a418cf3f5f1 ("x86/uaccess: Don't leak the AC flag into __put_user() value evaluation") Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings <[email protected]> --- arch/x86/include/asm/uaccess.h | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -422,10 +422,11 @@ do { \ #define __put_user_nocheck(x, ptr, size) \ ({ \ int __pu_err; \ - __typeof__(*(ptr)) __pu_val; \ - __pu_val = x; \ + __typeof__(*(ptr)) __pu_val = (x); \ + __typeof__(ptr) __pu_ptr = (ptr); \ + __typeof__(size) __pu_size = (size); \ __uaccess_begin(); \ - __put_user_size(__pu_val, (ptr), (size), __pu_err, -EFAULT); \ + __put_user_size(__pu_val, __pu_ptr, __pu_size, __pu_err, -EFAULT); \ __uaccess_end(); \ __pu_err; \ })
