This is a note to let you know that I've just added the patch titled btrfs: avoid double put of block group when emptying cluster to the 5.11-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: btrfs-avoid-double-put-of-block-group-when-emptying-cluster.patch and it can be found in the queue-5.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 95c85fba1f64c3249c67f0078a29f8a125078189 Mon Sep 17 00:00:00 2001 From: Josef Bacik <josef@xxxxxxxxxxxxxx> Date: Mon, 25 Jan 2021 16:42:35 -0500 Subject: btrfs: avoid double put of block group when emptying cluster From: Josef Bacik <josef@xxxxxxxxxxxxxx> commit 95c85fba1f64c3249c67f0078a29f8a125078189 upstream. 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@xxxxxxxxxxxxxxx # 4.4+ Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx> Reviewed-by: David Sterba <dsterba@xxxxxxxx> [ update changelog ] Signed-off-by: David Sterba <dsterba@xxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/btrfs/free-space-cache.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/fs/btrfs/free-space-cache.c +++ b/fs/btrfs/free-space-cache.c @@ -2708,8 +2708,10 @@ static void __btrfs_return_cluster_to_fr 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; @@ -2747,8 +2749,6 @@ static void __btrfs_return_cluster_to_fr entry->offset, &entry->offset_index, bitmap); } cluster->root = RB_ROOT; - -out: spin_unlock(&cluster->lock); btrfs_put_block_group(block_group); } Patches currently in stable-queue which might be from josef@xxxxxxxxxxxxxx are queue-5.11/btrfs-fix-race-between-extent-freeing-allocation-when-using-bitmaps.patch queue-5.11/btrfs-tree-checker-do-not-error-out-if-extent-ref-hash-doesn-t-match.patch queue-5.11/btrfs-fix-stale-data-exposure-after-cloning-a-hole-with-no_holes-enabled.patch queue-5.11/btrfs-avoid-double-put-of-block-group-when-emptying-cluster.patch queue-5.11/btrfs-fix-race-between-writes-to-swap-files-and-scrub.patch queue-5.11/btrfs-fix-race-between-swap-file-activation-and-snapshot-creation.patch