[PATCH 5.0 094/238] btrfs: drop the lock on error in btrfs_dev_replace_cancel

[Greg Kroah-Hartman]

5.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

commit 669e859b5ea7c6f4fce0149d3907c64e550c294b upstream.

We should drop the lock on this error path.  This has been found by a
static tool.

The lock needs to be released, it's there to protect access to the
dev_replace members and is not supposed to be left locked. The value of
state that's being switched would need to be artifically changed to an
invalid value so the default: branch is taken.

Fixes: d189dd70e255 ("btrfs: fix use-after-free due to race between replace start and cancel")
CC: stable@xxxxxxxxxxxxxxx # 5.0+
Reviewed-by: Anand Jain <anand.jain@xxxxxxxxxx>
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/btrfs/dev-replace.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -862,6 +862,7 @@ int btrfs_dev_replace_cancel(struct btrf
 			btrfs_destroy_dev_replace_tgtdev(tgt_device);
 		break;
 	default:
+		up_write(&dev_replace->rwsem);
 		result = -EINVAL;
 	}