[PATCH 09/16] FIX [1/2] slub: Do not dereference NULL pointer in node_match

From: Sebastian Andrzej Siewior
Date: Wed Feb 13 2013 - 11:13:27 EST

From: Christoph Lameter <cl@xxxxxxxxx>

The variables accessed in slab_alloc are volatile and therefore
the page pointer passed to node_match can be NULL. The processing
of data in slab_alloc is tentative until either the cmpxhchg
succeeds or the __slab_alloc slowpath is invoked. Both are
able to perform the same allocation from the freelist.

Check for the NULL pointer in node_match.

A false positive will lead to a retry of the loop in __slab_alloc.

Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
[bigeasy@linutronix: replace page with c->page]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
mm/slub.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/slub.c b/mm/slub.c
index 5710788..08eb4c1 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2038,7 +2038,7 @@ static void flush_all(struct kmem_cache *s)
static inline int node_match(struct kmem_cache_cpu *c, int node)
- if (node != NUMA_NO_NODE && c->node != node)
+ if (!c->page || (node != NUMA_NO_NODE && c->node != node))
return 0;
return 1;

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