[PATCH 4.19 05/37] btrfs: fix block group leak when removing fails

[Greg Kroah-Hartman]

From: Xiyu Yang <xiyuyan...@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: sta...@vger.kernel.org # 4.4+
Signed-off-by: Xiyu Yang <xiyuyan...@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin....@gmail.com>
Reviewed-by: David Sterba <dste...@suse.com>
Signed-off-by: David Sterba <dste...@suse.com>
Signed-off-by: Greg Kroah-Hartman <gre...@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
@@ -10286,7 +10286,7 @@ int btrfs_remove_block_group(struct btrf
        path = btrfs_alloc_path();
        if (!path) {
                ret = -ENOMEM;
-               goto out;
+               goto out_put_group;
        }
 
        /*
@@ -10323,7 +10323,7 @@ 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 */
@@ -10346,13 +10346,13 @@ 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);
        }
 
@@ -10494,9 +10494,9 @@ int btrfs_remove_block_group(struct btrf
 
        ret = remove_block_group_free_space(trans, 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);
@@ -10524,6 +10524,10 @@ int btrfs_remove_block_group(struct btrf
                /* once for the tree */
                free_extent_map(em);
        }
+
+out_put_group:
+       /* Once for the lookup reference */
+       btrfs_put_block_group(block_group);
 out:
        btrfs_free_path(path);
        return ret;