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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: fa9c0d795f ("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>
This commit is contained in:
Josef Bacik 2021-01-25 16:42:35 -05:00 committed by David Sterba
parent 3660d0bcdb
commit 95c85fba1f
1 changed files with 4 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
fs/btrfs/free-space-cache.c
View File

@ -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);
}