Commit 69abaffe authored by Konstantin Khlebnikov's avatar Konstantin Khlebnikov Committed by Jens Axboe

cfq-iosched: handle failure of cfq group allocation

Cfq_lookup_create_cfqg() allocates struct blkcg_gq using GFP_ATOMIC.
In cfq_find_alloc_queue() possible allocation failure is not handled.
As a result kernel oopses on NULL pointer dereference when
cfq_link_cfqq_cfqg() calls cfqg_get() for NULL pointer.

Bug was introduced in v3.5 in commit cd1604fa ("blkcg: factor
out blkio_group creation"). Prior to that commit cfq group lookup
had returned pointer to root group as fallback.

This patch handles this error using existing fallback oom_cfqq.
Signed-off-by: default avatarKonstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarVivek Goyal <vgoyal@redhat.com>
Fixes: cd1604fa ("blkcg: factor out blkio_group creation")
Cc: stable@kernel.org
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 9f9ee1f2
...@@ -3590,6 +3590,11 @@ cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic, ...@@ -3590,6 +3590,11 @@ cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
blkcg = bio_blkcg(bio); blkcg = bio_blkcg(bio);
cfqg = cfq_lookup_create_cfqg(cfqd, blkcg); cfqg = cfq_lookup_create_cfqg(cfqd, blkcg);
if (!cfqg) {
cfqq = &cfqd->oom_cfqq;
goto out;
}
cfqq = cic_to_cfqq(cic, is_sync); cfqq = cic_to_cfqq(cic, is_sync);
/* /*
...@@ -3626,7 +3631,7 @@ cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic, ...@@ -3626,7 +3631,7 @@ cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
} else } else
cfqq = &cfqd->oom_cfqq; cfqq = &cfqd->oom_cfqq;
} }
out:
if (new_cfqq) if (new_cfqq)
kmem_cache_free(cfq_pool, new_cfqq); kmem_cache_free(cfq_pool, new_cfqq);
......
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