From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753139AbeDTX7q (ORCPT ); Fri, 20 Apr 2018 19:59:46 -0400 Received: from mail.kernel.org ([198.145.29.99]:47246 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752778AbeDTX7M (ORCPT ); Fri, 20 Apr 2018 19:59:12 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 38C5821838 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=mcgrof@kernel.org From: "Luis R. Rodriguez" To: viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org Cc: jack@suse.cz, bart.vanassche@wdc.com, ming.lei@redhat.com, rjw@rjwysocki.net, mguzik@redhat.com, linux-pm@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, "Luis R. Rodriguez" Subject: [PATCH 3/3] fs: fix corner case race on freeze_bdev() when sb disappears Date: Fri, 20 Apr 2018 16:59:04 -0700 Message-Id: <20180420235904.27496-4-mcgrof@kernel.org> X-Mailer: git-send-email 2.13.2 In-Reply-To: <20180420235904.27496-1-mcgrof@kernel.org> References: <20180420235904.27496-1-mcgrof@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org freeze_bdev() will bail but leave the bd_fsfreeze_count incremented if the get_active_super() does not find the superblock on our super_blocks list to match. This issue has been present since v2.6.29 during the introduction of the ioctl_fsfreeze() and ioctl_fsthaw() via commit fcccf502540e3 ("filesystem freeze: implement generic freeze feature"). I am not aware of any existing races which have triggered this situation, however, if it does trigger it could mean leaving a superblock with bd_fsfreeze_count always positive. Fixes: fcccf502540e3 ("filesystem freeze: implement generic freeze feature") Signed-off-by: Luis R. Rodriguez --- fs/block_dev.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/block_dev.c b/fs/block_dev.c index b54966679833..7a532aa58c07 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -507,8 +507,10 @@ struct super_block *freeze_bdev(struct block_device *bdev) } sb = get_active_super(bdev); - if (!sb) + if (!sb) { + bdev->bd_fsfreeze_count--; goto out; + } if (sb->s_op->freeze_super) error = sb->s_op->freeze_super(sb); else -- 2.16.3