tree 0f1806d2aead6af9629bb701101b75b28863b986
parent adbbb8631beda8e4e5d2c964b8b47e04cfa0a2ae
author Miao Xie <miaox@cn.fujitsu.com> 1409751343 +0800
committer Chris Mason <clm@fb.com> 1410986324 -0700

Btrfs: fix use-after-free problem of the device during device replace

The problem is:
	Task0(device scan task)		Task1(device replace task)
	scan_one_device()
	mutex_lock(&uuid_mutex)
	device = find_device()
					mutex_lock(&device_list_mutex)
					lock_chunk()
					rm_and_free_source_device
					unlock_chunk()
					mutex_unlock(&device_list_mutex)
	check device

Destroying the target device if device replace fails also has the same problem.

We fix this problem by locking uuid_mutex during destroying source device or
target device, just like the device remove operation.

It is a temporary solution, we can fix this problem and make the code more
clear by atomic counter in the future.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>