Commit 69abaffe authored Feb 09, 2015 by Konstantin Khlebnikov Committed by Jens Axboe Feb 09, 2015

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: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Fixes: cd1604fa ("blkcg: factor out blkio_group creation")
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <axboe@fb.com>

parent 9f9ee1f2

block/cfq-iosched.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -3590,6 +3590,11 @@ cfq_find_alloc_queue(struct cfq_data cfqd, bool is_sync, struct cfq_io_cq cic,

		blkcg = bio_blkcg(bio);
		cfqg = cfq_lookup_create_cfqg(cfqd, blkcg);
		if (!cfqg) {
		cfqq = &cfqd->oom_cfqq;
		goto out;
		}

		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,
		} else
		cfqq = &cfqd->oom_cfqq;
		}

		out:
		if (new_cfqq)
		kmem_cache_free(cfq_pool, new_cfqq);