diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index ddf537923a0a..6ebae6bbe6a5 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -137,6 +137,9 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
 	if (kn_from == kn_to)
 		return strlcpy(buf, "/", buflen);
 
+	if (!buf)
+		return -EINVAL;
+
 	common = kernfs_common_ancestor(kn_from, kn_to);
 	if (WARN_ON(!common))
 		return -EINVAL;
@@ -144,8 +147,7 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
 	depth_to = kernfs_depth(common, kn_to);
 	depth_from = kernfs_depth(common, kn_from);
 
-	if (buf)
-		buf[0] = '\0';
+	buf[0] = '\0';
 
 	for (i = 0; i < depth_from; i++)
 		len += strlcpy(buf + len, parent_str,