From: Christoph Lameter cl@linux.com Subject: slab: alien caches must not be initialized if the allocation of the alien cache failed

Callers of __alloc_alien() check for NULL. We must do the same check in __alloc_alien_cache to avoid NULL pointer dereferences on allocation failures.

Link: http://lkml.kernel.org/r/010001680f42f192-82b4e12e-1565-4ee0-ae1f-1e98974906... Fixes: 49dfc304ba241 ("slab: use the lock on alien_cache, instead of the lock on array_cache") Fixes: c8522a3a5832b ("Slab: introduce alloc_alien") Signed-off-by: Christoph Lameter cl@linux.com Reported-by: syzbot+d6ed4ec679652b4fd4e4@syzkaller.appspotmail.com Reviewed-by: Andrew Morton akpm@linux-foundation.org Cc: Pekka Enberg penberg@kernel.org Cc: David Rientjes rientjes@google.com Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/slab.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/mm/slab.c~slab-alien-caches-must-not-be-initialized-if-the-allocation-of-the-alien-cache-failed +++ a/mm/slab.c @@ -666,8 +666,10 @@ static struct alien_cache *__alloc_alien struct alien_cache *alc = NULL;

alc = kmalloc_node(memsize, gfp, node); - init_arraycache(&alc->ac, entries, batch); - spin_lock_init(&alc->lock); + if (alc) { + init_arraycache(&alc->ac, entries, batch); + spin_lock_init(&alc->lock); + } return alc; }

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