btrfs: use after free in btrfs_quota_enable

The issue here is that btrfs_commit_transaction() frees "trans" on both
the error and the success path.  So the problem would be if
btrfs_commit_transaction() succeeds, and then qgroup_rescan_init()
fails.  That means that "ret" is non-zero and "trans" is non-NULL and it
leads to a use after free inside the btrfs_end_transaction() macro.

Fixes: 340f1aa27f36 ("btrfs: qgroups: Move transaction management inside btrfs_quota_enable/disable")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 4353bb6..d4917c0 100644 (file)
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -1019,10 +1019,9 @@ out_add_root:
        spin_unlock(&fs_info->qgroup_lock);
 
        ret = btrfs_commit_transaction(trans);
-       if (ret) {
-               trans = NULL;
+       trans = NULL;
+       if (ret)
                goto out_free_path;
-       }
 
        ret = qgroup_rescan_init(fs_info, 0, 1);
        if (!ret) {