Btrfs: fix unprotected device list access when cloning fs devices (adbbb863) · Commits · 戴 / test

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>

fs/btrfs/volumes.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -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);
		}

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