[PATCH 4.14 06/26] btrfs: fix block group leak when removing fails

Greg Kroah-Hartman
2020-05-04T18:00:54Z

From: Xiyu Yang <xiyuyang19@fudan.edu.cn>

commit f6033c5e333238f299c3ae03fac8cc1365b23b77 upstream.

btrfs_remove_block_group() invokes btrfs_lookup_block_group(), which
returns a local reference of the block group that contains the given
bytenr to "block_group" with increased refcount.

When btrfs_remove_block_group() returns, "block_group" becomes invalid,
so the refcount should be decreased to keep refcount balanced.

The reference counting issue happens in several exception handling paths
of btrfs_remove_block_group(). When those error scenarios occur such as
btrfs_alloc_path() returns NULL, the function forgets to decrease its
refcnt increased by btrfs_lookup_block_group() and will cause a refcnt
leak.

Fix this issue by jumping to "out_put_group" label and calling
btrfs_put_block_group() when those error scenarios occur.

CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.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>

---
fs/btrfs/extent-tree.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)

--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -10554,7 +10554,7 @@ int btrfs_remove_block_group(struct btrf
path = btrfs_alloc_path();
if (!path) {
ret = -ENOMEM;
- goto out;
+ goto out_put_group;
}

/*
@@ -10591,7 +10591,7 @@ int btrfs_remove_block_group(struct btrf
ret = btrfs_orphan_add(trans, BTRFS_I(inode));
if (ret) {
btrfs_add_delayed_iput(inode);
- goto out;
+ goto out_put_group;
}
clear_nlink(inode);
/* One for the block groups ref */
@@ -10614,13 +10614,13 @@ int btrfs_remove_block_group(struct btrf

ret = btrfs_search_slot(trans, tree_root, &key, path, -1, 1);
if (ret < 0)
- goto out;
+ goto out_put_group;
if (ret > 0)
btrfs_release_path(path);
if (ret == 0) {
ret = btrfs_del_item(trans, tree_root, path);
if (ret)
- goto out;
+ goto out_put_group;
btrfs_release_path(path);
}

@@ -10778,9 +10778,9 @@ int btrfs_remove_block_group(struct btrf

ret = remove_block_group_free_space(trans, fs_info, block_group);
if (ret)
- goto out;
+ goto out_put_group;

- btrfs_put_block_group(block_group);
+ /* Once for the block groups rbtree */
btrfs_put_block_group(block_group);

ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
@@ -10790,6 +10790,10 @@ int btrfs_remove_block_group(struct btrf
goto out;

ret = btrfs_del_item(trans, root, path);
+
+out_put_group:
+ /* Once for the lookup reference */
+ btrfs_put_block_group(block_group);
out:
btrfs_free_path(path);
return ret;