The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 95c85fba1f64c3249c67f0078a29f8a125078189 Mon Sep 17 00:00:00 2001
From: Josef Bacik josef@toxicpanda.com Date: Mon, 25 Jan 2021 16:42:35 -0500 Subject: [PATCH] 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: fa9c0d795f7b ("Btrfs: rework allocation clustering") CC: stable@vger.kernel.org # 4.4+ Signed-off-by: Josef Bacik josef@toxicpanda.com Reviewed-by: David Sterba dsterba@suse.com [ update changelog ] Signed-off-by: David Sterba dsterba@suse.com
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c index abcf951e6b44..711a6a751ae9 100644 --- a/fs/btrfs/free-space-cache.c +++ b/fs/btrfs/free-space-cache.c @@ -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); }