| Date | Wed, 28 Sep 2011 15:00:40 -0700 | From | Greg KH <> | Subject | [076/244] Avoid dereferencing a request_queue after last close. |
| |
3.0-stable review patch. If anyone has any objections, please let us know.
------------------
From: NeilBrown <neilb@suse.de>
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 <hch@lst.de> Cc: Hugh Dickins <hughd@google.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Wu Fengguang <fengguang.wu@intel.com> Acked-by: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- 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;
|