From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932317Ab1I1Wk4 (ORCPT ); Wed, 28 Sep 2011 18:40:56 -0400 Received: from cantor2.suse.de ([195.135.220.15]:53829 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932275Ab1I1Wkv (ORCPT ); Wed, 28 Sep 2011 18:40:51 -0400 X-Mailbox-Line: From gregkh@clark.kroah.org Wed Sep 28 15:01:33 2011 Message-Id: <20110928220133.310706786@clark.kroah.org> User-Agent: quilt/0.48-16.4 Date: Wed, 28 Sep 2011 15:00:40 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Christoph Hellwig , Hugh Dickins , Wu Fengguang , NeilBrown Subject: [076/244] Avoid dereferencing a request_queue after last close. In-Reply-To: <20110928220225.GA27128@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.0-stable review patch. If anyone has any objections, please let us know. ------------------ From: NeilBrown commit 94007751bb02797ba87bac7aacee2731ac2039a3 upstream. On the last close of an 'md' device which as been stopped, the device is destroyed and in particular the request_queue is freed. The free is done in a separate thread so it might happen a short time later. __blkdev_put calls bdev_inode_switch_bdi *after* ->release has been called. Since commit f758eeabeb96f878c860e8f110f94ec8820822a9 bdev_inode_switch_bdi will dereference the 'old' bdi, which lives inside a request_queue, to get a spin lock. This causes the last close on an md device to sometime take a spin_lock which lives in freed memory - which results in an oops. So move the called to bdev_inode_switch_bdi before the call to ->release. Cc: Christoph Hellwig Cc: Hugh Dickins Cc: Andrew Morton Cc: Wu Fengguang Acked-by: Wu Fengguang Signed-off-by: NeilBrown Signed-off-by: Greg Kroah-Hartman --- fs/block_dev.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -1419,6 +1419,11 @@ static int __blkdev_put(struct block_dev WARN_ON_ONCE(bdev->bd_holders); sync_blockdev(bdev); kill_bdev(bdev); + /* ->release can cause the old bdi to disappear, + * so must switch it out first + */ + bdev_inode_switch_bdi(bdev->bd_inode, + &default_backing_dev_info); } if (bdev->bd_contains == bdev) { if (disk->fops->release) @@ -1432,8 +1437,6 @@ static int __blkdev_put(struct block_dev disk_put_part(bdev->bd_part); bdev->bd_part = NULL; bdev->bd_disk = NULL; - bdev_inode_switch_bdi(bdev->bd_inode, - &default_backing_dev_info); if (bdev != bdev->bd_contains) victim = bdev->bd_contains; bdev->bd_contains = NULL;