From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 20 Feb 2013 19:06:20 +0000 (-0500)
Subject: btrfs: Init io_lock after cloning btrfs device struct
X-Git-Tag: v3.2.41~80
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=554995ab65f98584d95e06e4d44f0c4d3293cee7;p=thirdparty%2Fkernel%2Fstable.git

btrfs: Init io_lock after cloning btrfs device struct

commit 1cba0cdf5e4dbcd9e5fa5b54d7a028e55e2ca057 upstream.

__btrfs_close_devices() clones btrfs device structs with
memcpy(). Some of the fields in the clone are reinitialized, but it's
missing to init io_lock. In mainline this goes unnoticed, but on RT it
leaves the plist pointing to the original about to be freed lock
struct.

Initialize io_lock after cloning, so no references to the original
struct are left.

Reported-and-tested-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index f4b839fd3c9dd..d544035f6966f 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -543,6 +543,7 @@ static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
 		new_device->writeable = 0;
 		new_device->in_fs_metadata = 0;
 		new_device->can_discard = 0;
+		spin_lock_init(&new_device->io_lock);
 		list_replace_rcu(&device->dev_list, &new_device->dev_list);
 
 		call_rcu(&device->rcu, free_device);