[PATCH v2 16/16] slab: Restore __alloc_size attribute to __kmalloc_track_caller

[Kees Cook]

With skbuff's post-allocation use of ksize() rearranged to use
kmalloc_size_round() prior to allocation, the compiler can correctly
reason about the size of these allocations. The prior mismatch had caused
buffer overflow mitigations to erroneously fire under CONFIG_UBSAN_BOUNDS,
requiring a partial revert of the __alloc_size attributes. Restore the
attribute that had been removed in commit 93dd04ab0b2b ("slab: remove
__alloc_size attribute from __kmalloc_track_caller").

Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 include/linux/slab.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 727640173568..297b85ed2c29 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -693,7 +693,8 @@ static inline __alloc_size(1, 2) void *kcalloc(size_t n, size_t size, gfp_t flag
  * allocator where we care about the real place the memory allocation
  * request comes from.
  */
-extern void *__kmalloc_track_caller(size_t size, gfp_t flags, unsigned long caller);
+extern void *__kmalloc_track_caller(size_t size, gfp_t flags, unsigned long caller)
+				   __alloc_size(1);
 #define kmalloc_track_caller(size, flags) \
 	__kmalloc_track_caller(size, flags, _RET_IP_)
 
-- 
2.34.1