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Commit 9ab0c653 authored by Anand Jain's avatar Anand Jain Committed by Greg Kroah-Hartman
Browse files

btrfs: harden identification of a stale device 



commit 770c79fb65506fc7c16459855c3839429f46cb32 upstream.

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>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 4e5ba186

fs/btrfs/volumes.c

+37 −7
Original line number Diff line number Diff line
@@ -713,15 +713,47 @@ static void pending_bios_fn(struct btrfs_work *work) 
	run_scheduled_bios(device);

}



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;

	struct block_device *bdev_old;

	struct block_device *bdev_new;



	/*

	 * 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;

	bdev_old = lookup_bdev(device_name);

	kfree(device_name);

	if (IS_ERR(bdev_old))

		return false;



	bdev_new = lookup_bdev(path);

	if (IS_ERR(bdev_new))

		return false;



	if (bdev_old == bdev_new)

		return true;



	return false;

}



/*
@@ -754,9 +786,7 @@ 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 */