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cfq-iosched: handle failure of cfq group allocation

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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 cd1604fab4 ("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: cd1604fab4 ("blkcg: factor out blkio_group creation")
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Konstantin Khlebnikov 2015-02-09 16:42:49 +03:00 committed by Jens Axboe
parent 9f9ee1f2b2
commit 69abaffec7
1 changed files with 6 additions and 1 deletions
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7
block/cfq-iosched.c
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@ -3590,6 +3590,11 @@ retry:
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 @@ retry:
} else
cfqq = &cfqd->oom_cfqq;
}
out:
if (new_cfqq)
kmem_cache_free(cfq_pool, new_cfqq);