[PATCH 2/2] slab, kmemleak, bugfix, pass the correct pointer to kmemleak_erase()

[J. R. Okajima]

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

Cc: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>

Signed-off-by: J. R. Okajima <hooanon05@xxxxxxxxxxx>
---
 mm/slab.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index 4e61449..66e9047 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
-- 
1.6.1.284.g5dc13

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