From adbbb8631beda8e4e5d2c964b8b47e04cfa0a2ae Mon Sep 17 00:00:00 2001 From: Miao Xie Date: Wed, 3 Sep 2014 21:35:42 +0800 Subject: [PATCH] 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 Signed-off-by: Chris Mason --- fs/btrfs/volumes.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 105c5fe..d28e176 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -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); } -- 2.7.4