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Btrfs: fix unprotected device list access when cloning fs devices 

We can build a new filesystem based a seed filesystem, and we need clone
the fs devices when we open the new filesystem. But someone might clear
the seed flag of the seed filesystem, then mount that filesystem and
remove some device. If we mount the new filesystem, we might access
a device list which was being changed when we clone the fs devices.
Fix it.

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 21:35:42 +08:00 committed by Chris Mason
parent 2196d6e8a7
commit adbbb8631b
1 changed files with 3 additions and 0 deletions
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3
fs/btrfs/volumes.c
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@ -583,6 +583,7 @@ static struct btrfs_fs_devices *clone_fs_devices(struct btrfs_fs_devices *orig)
if (IS_ERR(fs_devices))
return fs_devices;
mutex_lock(&orig->device_list_mutex);
fs_devices->total_devices = orig->total_devices;
/* We have held the volume lock, it is safe to get the devices. */
@ -611,8 +612,10 @@ static struct btrfs_fs_devices *clone_fs_devices(struct btrfs_fs_devices *orig)
device->fs_devices = fs_devices;
fs_devices->num_devices++;
}
mutex_unlock(&orig->device_list_mutex);
return fs_devices;
error:
mutex_unlock(&orig->device_list_mutex);
free_fs_devices(fs_devices);
return ERR_PTR(-ENOMEM);
}