slub: Do not dereference NULL pointer in node_match
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@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
diff --git a/mm/slub.c b/mm/slub.c
index 21b3f00..8b1b99d 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2042,7 +2042,7 @@
static inline int node_match(struct page *page, int node)
{
#ifdef CONFIG_NUMA
- if (node != NUMA_NO_NODE && page_to_nid(page) != node)
+ if (!page || (node != NUMA_NO_NODE && page_to_nid(page) != node))
return 0;
#endif
return 1;