4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Christoph Lameter <cl@xxxxxxxxx> 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-000000@xxxxxxxxxxxxxxxxxxx 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@xxxxxxxxx> Reported-by: syzbot+d6ed4ec679652b4fd4e4@xxxxxxxxxxxxxxxxxxxxxxxxx Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/slab.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/mm/slab.c +++ b/mm/slab.c @@ -875,8 +875,10 @@ 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; }
