From 69abaffec7d47a083739b79e3066cb3730eba72e Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Mon, 9 Feb 2015 16:42:49 +0300 Subject: [PATCH] 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 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 Acked-by: Tejun Heo Acked-by: Vivek Goyal Fixes: cd1604fab4f9 ("blkcg: factor out blkio_group creation") Cc: stable@kernel.org Signed-off-by: Jens Axboe --- 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 b9abdca84c17..5da8e6e9ab4b 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -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);