Btrfs: fix qgroup double free after failure to reserve metadata for delalloc

BugLink: https://bugs.launchpad.net/bugs/1850456
commit c7967fc1499beb9b70bb9d33525fb0b384af8883 upstream.

If we fail to reserve metadata for delalloc operations we end up releasing
the previously reserved qgroup amount twice, once explicitly under the
'out_qgroup' label by calling btrfs_qgroup_free_meta_prealloc() and once
again, under label 'out_fail', by calling btrfs_inode_rsv_release() with a
value of 'true' for its 'qgroup_free' argument, which results in
btrfs_qgroup_free_meta_prealloc() being called again, so we end up having
a double free.

Also if we fail to reserve the necessary qgroup amount, we jump to the
label 'out_fail', which calls btrfs_inode_rsv_release() and that in turns
calls btrfs_qgroup_free_meta_prealloc(), even though we weren't able to
reserve any qgroup amount. So we freed some amount we never reserved.

So fix this by removing the call to btrfs_inode_rsv_release() in the
failure path, since it's not necessary at all as we haven't changed the
inode's block reserve in any way at this point.

Fixes: c8eaeac7b73434 ("btrfs: reserve delalloc metadata differently")
CC: stable@vger.kernel.org # 5.2+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/fs/btrfs/delalloc-space.c b/fs/btrfs/delalloc-space.c
index 17f7c0d3876850087c27f43fbec84aa02a559ab1..934521fe7e71ddfe3e6647cee70f8bc7bd2e6573 100644 (file)
--- a/fs/btrfs/delalloc-space.c
+++ b/fs/btrfs/delalloc-space.c
@@ -371,7 +371,6 @@ int btrfs_delalloc_reserve_metadata(struct btrfs_inode *inode, u64 num_bytes)
 out_qgroup:
        btrfs_qgroup_free_meta_prealloc(root, qgroup_reserve);
 out_fail:
-       btrfs_inode_rsv_release(inode, true);
        if (delalloc_lock)
                mutex_unlock(&inode->delalloc_mutex);
        return ret;