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    Subject[PATCH 4.14 13/27] slab: alien caches must not be initialized if the allocation of the alien cache failed
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

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

    From: Christoph Lameter <cl@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-000000@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 <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>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@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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