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authorNeilBrown <neilb@suse.de>2011-09-10 17:20:21 +1000
committerNeilBrown <neilb@suse.de>2011-09-10 17:20:21 +1000
commit94007751bb02797ba87bac7aacee2731ac2039a3 (patch)
treeac45ec9aef327e0a77f3ffd8c09eff9ef1609f95
parent43220aa0f22cd3ce5b30246d50ccd696d119edea (diff)
downloadlinux-stericsson-94007751bb02797ba87bac7aacee2731ac2039a3.tar.gz
Avoid dereferencing a 'request_queue' after last close.
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> Cc: stable@kernel.org Signed-off-by: NeilBrown <neilb@suse.de>
-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 ff77262e887c..95f786ec7f08 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1429,6 +1429,11 @@ 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)
@@ -1442,8 +1447,6 @@ 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;