From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751925AbdBXIoc (ORCPT ); Fri, 24 Feb 2017 03:44:32 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:58690 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751973AbdBXIlF (ORCPT ); Fri, 24 Feb 2017 03:41:05 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tejun Heo , Dmitry Vyukov , Jens Axboe Subject: [PATCH 4.10 19/21] block: fix double-free in the failure path of cgwb_bdi_init() Date: Fri, 24 Feb 2017 09:40:18 +0100 Message-Id: <20170224083852.141357604@linuxfoundation.org> X-Mailer: git-send-email 2.11.1 In-Reply-To: <20170224083851.364707301@linuxfoundation.org> References: <20170224083851.364707301@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tejun Heo commit 5f478e4ea5c5560b4e40eb136991a09f9389f331 upstream. When !CONFIG_CGROUP_WRITEBACK, bdi has single bdi_writeback_congested at bdi->wb_congested. cgwb_bdi_init() allocates it with kzalloc() and doesn't do further initialization. This usually works fine as the reference count gets bumped to 1 by wb_init() and the put from wb_exit() releases it. However, when wb_init() fails, it puts the wb base ref automatically freeing the wb and the explicit kfree() in cgwb_bdi_init() error path ends up trying to free the same pointer the second time causing a double-free. Fix it by explicitly initilizing the refcnt to 1 and putting the base ref from cgwb_bdi_destroy(). Signed-off-by: Tejun Heo Reported-by: Dmitry Vyukov Fixes: a13f35e87140 ("writeback: don't embed root bdi_writeback_congested in bdi_writeback") Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- mm/backing-dev.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -758,15 +758,20 @@ static int cgwb_bdi_init(struct backing_ if (!bdi->wb_congested) return -ENOMEM; + atomic_set(&bdi->wb_congested->refcnt, 1); + err = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL); if (err) { - kfree(bdi->wb_congested); + wb_congested_put(bdi->wb_congested); return err; } return 0; } -static void cgwb_bdi_destroy(struct backing_dev_info *bdi) { } +static void cgwb_bdi_destroy(struct backing_dev_info *bdi) +{ + wb_congested_put(bdi->wb_congested); +} #endif /* CONFIG_CGROUP_WRITEBACK */