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authorNeilBrown <neilb@suse.de>2011-09-10 17:20:21 +1000
committerGreg Kroah-Hartman <gregkh@suse.de>2011-10-03 11:40:14 -0700
commit97e5a85664252fd3f3f84751c7779c326df9c851 (patch)
treebecfedf06d19a4f65aa1789442c1f4268f10b9c8 /fs
parent045451f9de4d9b7a7a961bf2428b990edf543271 (diff)
Avoid dereferencing a 'request_queue' after last close.
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>
Diffstat (limited to 'fs')
-rw-r--r--fs/block_dev.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 610e8e0b04b..194cf66bc8f 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1419,6 +1419,11 @@ static int __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
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_device *bdev, fmode_t mode, int for_part)
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;