Commit 95c85fba authored by Josef Bacik's avatar Josef Bacik Committed by David Sterba
Browse files

btrfs: avoid double put of block group when emptying cluster 



It's wrong calling btrfs_put_block_group in
__btrfs_return_cluster_to_free_space if the block group passed is
different than the block group the cluster represents. As this means the
cluster doesn't have a reference to the passed block group. This results
in double put and a use-after-free bug.

Fix this by simply bailing if the block group we passed in does not
match the block group on the cluster.

Fixes: fa9c0d79 ("Btrfs: rework allocation clustering")
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: default avatarJosef Bacik <josef@toxicpanda.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 3660d0bc

fs/btrfs/free-space-cache.c

+4 −4
Original line number Diff line number Diff line
@@ -2801,8 +2801,10 @@ static void __btrfs_return_cluster_to_free_space( 
	struct rb_node *node;



	spin_lock(&cluster->lock);

	if (cluster->block_group != block_group)

		goto out;

	if (cluster->block_group != block_group) {

		spin_unlock(&cluster->lock);

		return;

	}



	cluster->block_group = NULL;

	cluster->window_start = 0;
@@ -2840,8 +2842,6 @@ static void __btrfs_return_cluster_to_free_space( 
				   entry->offset, &entry->offset_index, bitmap);

	}

	cluster->root = RB_ROOT;



out:

	spin_unlock(&cluster->lock);

	btrfs_put_block_group(block_group);

}