[PATCH 09/20] btrfs: export: handle invalid inode or root reference in btrfs_get_parent()

[David Sterba <dsterba@suse.com>]

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).

Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/export.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/export.c b/fs/btrfs/export.c
index 744a02b7fd67..203e5964c9b0 100644
--- a/fs/btrfs/export.c
+++ b/fs/btrfs/export.c
@@ -174,8 +174,15 @@ 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;
-- 
2.42.1