4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Christoph Lameter <c...@linux.com>

commit 09c2e76ed734a1d36470d257a778aaba28e86531 upstream.

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-1e98974906aa-000...@email.amazonses.com
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 <c...@linux.com>
Reported-by: syzbot+d6ed4ec679652b4fd...@syzkaller.appspotmail.com
Reviewed-by: Andrew Morton <a...@linux-foundation.org>
Cc: Pekka Enberg <penb...@kernel.org>
Cc: David Rientjes <rient...@google.com>
Cc: Joonsoo Kim <iamjoonsoo....@lge.com>
Cc: <sta...@vger.kernel.org>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

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

--- a/mm/slab.c
+++ b/mm/slab.c
@@ -679,8 +679,10 @@ 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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