Btrfs: open_ctree() error handling can oops on fs_info

a bug in open_ctree:

struct btrfs_root *open_ctree(..)
{
....
	if (!extent_root || !tree_root || !fs_info ||
	    !chunk_root || !dev_root || !csum_root) {
		err = -ENOMEM;
		goto fail;
//When code flow goes to "fail", fs_info may be NULL or uninitialized.
	}
....

fail:
	btrfs_close_devices(fs_info->fs_devices);// !
	btrfs_mapping_tree_free(&fs_info->mapping_tree);// !

	kfree(extent_root);
	kfree(tree_root);
	bdi_destroy(&fs_info->bdi);// !
...
)

Signed-off-by: Qinghuang Feng <qhfeng.kernel@gmail.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 26a18779e84b..3cf17257f89d 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1823,13 +1823,14 @@ fail_sb_buffer:
 fail_iput:
         invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
         iput(fs_info->btree_inode);
-fail:
+
         btrfs_close_devices(fs_info->fs_devices);
         btrfs_mapping_tree_free(&fs_info->mapping_tree);
+        bdi_destroy(&fs_info->bdi);
 
+fail:
         kfree(extent_root);
         kfree(tree_root);
-        bdi_destroy(&fs_info->bdi);
         kfree(fs_info);
         kfree(chunk_root);
         kfree(dev_root);