From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754863AbbCFKgX (ORCPT ); Fri, 6 Mar 2015 05:36:23 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:44358 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751057AbbCFJ73 (ORCPT ); Fri, 6 Mar 2015 04:59:29 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Konstantin Khlebnikov , Jens Axboe , Luis Henriques Subject: [PATCH 3.16.y-ckt 089/183] cfq-iosched: handle failure of cfq group allocation Date: Fri, 6 Mar 2015 09:56:20 +0000 Message-Id: <1425635874-19087-90-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1425635874-19087-1-git-send-email-luis.henriques@canonical.com> References: <1425635874-19087-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.7-ckt8 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Konstantin Khlebnikov 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 Acked-by: Tejun Heo Acked-by: Vivek Goyal Fixes: cd1604fab4f9 ("blkcg: factor out blkio_group creation") Signed-off-by: Jens Axboe Signed-off-by: Luis Henriques --- 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);