From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935693Ab1KJDeA (ORCPT ); Wed, 9 Nov 2011 22:34:00 -0500 Received: from cantor2.suse.de ([195.135.220.15]:43219 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935655Ab1KJDd4 (ORCPT ); Wed, 9 Nov 2011 22:33:56 -0500 X-Mailbox-Line: From gregkh@clark.kroah.org Wed Nov 9 13:27:23 2011 Message-Id: <20111109212723.217993801@clark.kroah.org> User-Agent: quilt/0.48-16.4 Date: Wed, 09 Nov 2011 13:29:07 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Tejun Heo , Jens Axboe Subject: [225/262] block: make gendisk hold a reference to its queue In-Reply-To: <20111109212847.GA20838@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 me know. ------------------ From: Tejun Heo commit f992ae801a7dec34a4ed99a6598bbbbfb82af4fb upstream. The following command sequence triggers an oops. # mount /dev/sdb1 /mnt # echo 1 > /sys/class/scsi_device/0\:0\:1\:0/device/delete # umount /mnt general protection fault: 0000 [#1] PREEMPT SMP CPU 2 Modules linked in: Pid: 791, comm: umount Not tainted 3.1.0-rc3-work+ #8 Bochs Bochs RIP: 0010:[] [] __lock_acquire+0x389/0x1d60 ... Call Trace: [] lock_acquire+0x95/0x140 [] _raw_spin_lock+0x3b/0x50 [] bdi_lock_two+0x5c/0x70 [] bdev_inode_switch_bdi+0x4c/0xf0 [] __blkdev_put+0x11b/0x1d0 [] __blkdev_put+0x160/0x1d0 [] blkdev_put+0x5f/0x190 [] kill_block_super+0x4d/0x80 [] deactivate_locked_super+0x45/0x70 [] deactivate_super+0x4a/0x70 [] mntput_no_expire+0xed/0x130 [] sys_umount+0x7e/0x3a0 [] system_call_fastpath+0x16/0x1b This is because bdev holds on to disk but disk doesn't pin the associated queue. If a SCSI device is removed while the device is still open, the sdev puts the base reference to the queue on release. When the bdev is finally released, the associated queue is already gone along with the bdi and bdev_inode_switch_bdi() ends up dereferencing already freed bdi. Even if it were not for this bug, disk not holding onto the associated queue is very unusual and error-prone. Fix it by making add_disk() take an extra reference to its queue and put it on disk_release() and ensuring that disk and its fops owner are put in that order after all accesses to the disk and queue are complete. Signed-off-by: Tejun Heo Cc: Jens Axboe Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/genhd.c | 8 ++++++++ fs/block_dev.c | 13 ++++++++----- 2 files changed, 16 insertions(+), 5 deletions(-) --- a/block/genhd.c +++ b/block/genhd.c @@ -611,6 +611,12 @@ void add_disk(struct gendisk *disk) register_disk(disk); blk_register_queue(disk); + /* + * Take an extra ref on queue which will be put on disk_release() + * so that it sticks around as long as @disk is there. + */ + WARN_ON_ONCE(blk_get_queue(disk->queue)); + retval = sysfs_create_link(&disk_to_dev(disk)->kobj, &bdi->dev->kobj, "bdi"); WARN_ON(retval); @@ -1103,6 +1109,8 @@ static void disk_release(struct device * disk_replace_part_tbl(disk, NULL); free_part_stats(&disk->part0); free_part_info(&disk->part0); + if (disk->queue) + blk_put_queue(disk->queue); kfree(disk); } struct class block_class = { --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -1075,6 +1075,7 @@ static int __blkdev_put(struct block_dev static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) { struct gendisk *disk; + struct module *owner; int ret; int partno; int perm = 0; @@ -1100,6 +1101,7 @@ static int __blkdev_get(struct block_dev disk = get_gendisk(bdev->bd_dev, &partno); if (!disk) goto out; + owner = disk->fops->owner; disk_block_events(disk); mutex_lock_nested(&bdev->bd_mutex, for_part); @@ -1127,8 +1129,8 @@ static int __blkdev_get(struct block_dev bdev->bd_disk = NULL; mutex_unlock(&bdev->bd_mutex); disk_unblock_events(disk); - module_put(disk->fops->owner); put_disk(disk); + module_put(owner); goto restart; } } @@ -1184,8 +1186,8 @@ static int __blkdev_get(struct block_dev goto out_unlock_bdev; } /* only one opener holds refs to the module and disk */ - module_put(disk->fops->owner); put_disk(disk); + module_put(owner); } bdev->bd_openers++; if (for_part) @@ -1205,8 +1207,8 @@ static int __blkdev_get(struct block_dev out_unlock_bdev: mutex_unlock(&bdev->bd_mutex); disk_unblock_events(disk); - module_put(disk->fops->owner); put_disk(disk); + module_put(owner); out: bdput(bdev); @@ -1432,14 +1434,15 @@ static int __blkdev_put(struct block_dev if (!bdev->bd_openers) { struct module *owner = disk->fops->owner; - put_disk(disk); - module_put(owner); disk_put_part(bdev->bd_part); bdev->bd_part = NULL; bdev->bd_disk = NULL; if (bdev != bdev->bd_contains) victim = bdev->bd_contains; bdev->bd_contains = NULL; + + put_disk(disk); + module_put(owner); } mutex_unlock(&bdev->bd_mutex); bdput(bdev);