slab, kmemleak: pass the correct pointer to kmemleak_erase()

In ____cache_alloc(), the variable 'ac' may be changed after
cache_alloc_refill() and the following kmemleak_erase() may get an incorrect
pointer. Update 'ac' after cache_alloc_refill() unconditionally.

See the following URL for the discussion of this patch:

 http://marc.info/?l=linux-kernel&m=125873373124187&w=2

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: J. R. Okajima <hooanon05@yahoo.co.jp>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

1 files changed, 5 insertions, 0 deletions

diff --git a/mm/slab.c b/mm/slab.c
index 4e61449d7946..66e90477a4bb 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3103,6 +3103,11 @@ static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
         } else {
                 STATS_INC_ALLOCMISS(cachep);
                 objp = cache_alloc_refill(cachep, flags);
+                /*
+                 * the 'ac' may be updated by cache_alloc_refill(),
+                 * and kmemleak_erase() requires its correct value.
+                 */
+                ac = cpu_cache_get(cachep);
         }
         /*
          * To avoid a false negative, if an object that is in one of the