btrfs: export: handle invalid inode or root reference in btrfs_get_parent()

The get_parent handler looks up a parent of a given dentry, this can be
either a subvolume or a directory. The search is set up with offset -1
but it's never expected to find such item, as it would break allowed
range of inode number or a root id. This means it's a corruption (ext4
also returns this error code).

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/export.c b/fs/btrfs/export.c
index 3f2e8fb9e3e9504bd9e6eb18559d0af8d423cd1f..d710339ca4f391babd58ba835492c8d38d0c4abc 100644 (file)
--- a/fs/btrfs/export.c
+++ b/fs/btrfs/export.c
@@ -173,8 +173,15 @@ struct dentry *btrfs_get_parent(struct dentry *child)
        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                goto fail;
+       if (ret == 0) {
+               /*
+                * Key with offset of -1 found, there would have to exist an
+                * inode with such number or a root with such id.
+                */
+               ret = -EUCLEAN;
+               goto fail;
+       }
 
-       BUG_ON(ret == 0); /* Key with offset of -1 found */
        if (path->slots[0] == 0) {
                ret = -ENOENT;
                goto fail;