From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932661AbbBINmy (ORCPT ); Mon, 9 Feb 2015 08:42:54 -0500 Received: from forward-corp1f.mail.yandex.net ([95.108.130.40]:57284 "EHLO forward-corp1f.mail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932484AbbBINmx (ORCPT ); Mon, 9 Feb 2015 08:42:53 -0500 Authentication-Results: smtpcorp1m.mail.yandex.net; dkim=pass header.i=@yandex-team.ru Subject: [PATCH] cfq-iosched: handle failure of cfq group allocation From: Konstantin Khlebnikov To: Jens Axboe , linux-kernel@vger.kernel.org Cc: Tejun Heo , Vivek Goyal , stable@vger.kernel.org Date: Mon, 09 Feb 2015 16:42:49 +0300 Message-ID: <20150209134249.12420.97482.stgit@buzz> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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 6f2751d..01898a4 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);