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linux-sg2042
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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>
This commit is contained in:
Miao Xie 2014-09-03 21:35:43 +08:00 committed by Chris Mason
parent adbbb8631b
commit 67a2c45ee7
3 changed files with 8 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
fs/btrfs/dev-replace.c
View File

@ -509,6 +509,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
ret = btrfs_commit_transaction(trans, root);
WARN_ON(ret);
mutex_lock(&uuid_mutex);
/* keep away write_all_supers() during the finishing procedure */
mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
mutex_lock(&root->fs_info->chunk_mutex);
@ -536,6 +537,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
btrfs_dev_replace_unlock(dev_replace);
mutex_unlock(&root->fs_info->chunk_mutex);
mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
mutex_unlock(&uuid_mutex);
if (tgt_device)
btrfs_destroy_dev_replace_tgtdev(fs_info, tgt_device);
mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
@ -591,6 +593,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
*/
mutex_unlock(&root->fs_info->chunk_mutex);
mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
mutex_unlock(&uuid_mutex);
/* write back the superblocks */
trans = btrfs_start_transaction(root, 0);

4
fs/btrfs/volumes.c
View File

@ -50,7 +50,7 @@ static void __btrfs_reset_dev_stats(struct btrfs_device *dev);
static void btrfs_dev_stat_print_on_error(struct btrfs_device *dev);
static void btrfs_dev_stat_print_on_load(struct btrfs_device *device);
static DEFINE_MUTEX(uuid_mutex);
DEFINE_MUTEX(uuid_mutex);
static LIST_HEAD(fs_uuids);
static void lock_chunks(struct btrfs_root *root)
@ -1867,6 +1867,7 @@ void btrfs_destroy_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
{
struct btrfs_device *next_device;
mutex_lock(&uuid_mutex);
WARN_ON(!tgtdev);
mutex_lock(&fs_info->fs_devices->device_list_mutex);
if (tgtdev->bdev) {
@ -1886,6 +1887,7 @@ void btrfs_destroy_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
call_rcu(&tgtdev->rcu, free_device);
mutex_unlock(&fs_info->fs_devices->device_list_mutex);
mutex_unlock(&uuid_mutex);
}
static int btrfs_find_device_by_path(struct btrfs_root *root, char *device_path,

2
fs/btrfs/volumes.h
View File

@ -24,6 +24,8 @@
#include <linux/btrfs.h>
#include "async-thread.h"
extern struct mutex uuid_mutex;
#define BTRFS_STRIPE_LEN (64 * 1024)
struct buffer_head;