Commit 770c79fb authored by Anand Jain's avatar Anand Jain Committed by David Sterba
Browse files

btrfs: harden identification of a stale device 



Identifying and removing the stale device from the fs_uuids list is done
by btrfs_free_stale_devices().  btrfs_free_stale_devices() in turn
depends on device_path_matched() to check if the device appears in more
than one btrfs_device structure.

The matching of the device happens by its path, the device path. However,
when device mapper is in use, the dm device paths are nothing but a link
to the actual block device, which leads to the device_path_matched()
failing to match.

Fix this by matching the dev_t as provided by lookup_bdev() instead of
plain string compare of the device paths.

Reported-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarAnand Jain <anand.jain@oracle.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent bef16b52

fs/btrfs/volumes.c

+38 −7
Original line number Diff line number Diff line
@@ -534,15 +534,48 @@ btrfs_get_bdev_and_sb(const char *device_path, fmode_t flags, void *holder, 
	return ret;

}



static bool device_path_matched(const char *path, struct btrfs_device *device)

/*

 * Check if the device in the path matches the device in the given struct device.

 *

 * Returns:

 *   true  If it is the same device.

 *   false If it is not the same device or on error.

 */

static bool device_matched(const struct btrfs_device *device, const char *path)

{

	int found;

	char *device_name;

	dev_t dev_old;

	dev_t dev_new;

	int ret;



	/*

	 * If we are looking for a device with the matching dev_t, then skip

	 * device without a name (a missing device).

	 */

	if (!device->name)

		return false;



	device_name = kzalloc(BTRFS_PATH_NAME_MAX, GFP_KERNEL);

	if (!device_name)

		return false;



	rcu_read_lock();

	found = strcmp(rcu_str_deref(device->name), path);

	scnprintf(device_name, BTRFS_PATH_NAME_MAX, "%s", rcu_str_deref(device->name));

	rcu_read_unlock();



	return found == 0;

	ret = lookup_bdev(device_name, &dev_old);

	kfree(device_name);

	if (ret)

		return false;



	ret = lookup_bdev(path, &dev_new);

	if (ret)

		return false;



	if (dev_old == dev_new)

		return true;



	return false;

}



/*
@@ -575,9 +608,7 @@ static int btrfs_free_stale_devices(const char *path, 
					 &fs_devices->devices, dev_list) {

			if (skip_device && skip_device == device)

				continue;

			if (path && !device->name)

				continue;

			if (path && !device_path_matched(path, device))

			if (path && !device_matched(device, path))

				continue;

			if (fs_devices->opened) {

				/* for an already deleted device return 0 */