lkml.org 
[lkml]   [2015]   [Mar]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 3.16.y-ckt 089/183] cfq-iosched: handle failure of cfq group allocation
Date
3.16.7-ckt8 -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: Luis Henriques <luis.henriques@canonical.com>
---
block/cfq-iosched.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index f3627ca9303b..2c0585adfaea 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -3582,6 +3582,11 @@ 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);

/*
@@ -3618,7 +3623,7 @@ retry:
} else
cfqq = &cfqd->oom_cfqq;
}
-
+out:
if (new_cfqq)
kmem_cache_free(cfq_pool, new_cfqq);


\
 
 \ /
  Last update: 2015-03-06 11:41    [W:0.454 / U:0.292 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site