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[3.13.y-ckt,074/143] cfq-iosched: handle failure of cfq group allocation

Message ID 1427831308-1854-75-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa March 31, 2015, 7:47 p.m. UTC 
3.13.11-ckt18 -stable review patch.  If anyone has any objections, please let me know.

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

From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>

commit 69abaffec7d47a083739b79e3066cb3730eba72e upstream.

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 cd1604fab4f9 ("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: cd1604fab4f9 ("blkcg: factor out blkio_group creation")
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 block/cfq-iosched.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
diff mbox

Patch

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index b8fb8bf..e13e06d 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -3600,6 +3600,11 @@  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);
 
 	/*
@@ -3636,7 +3641,7 @@  retry:
 		} else
 			cfqq = &cfqd->oom_cfqq;
 	}
-
+out:
 	if (new_cfqq)
 		kmem_cache_free(cfq_pool, new_cfqq);