Re: [syzbot] WARNING in ovl_create_real

[Miklos Szeredi]

#syz test git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
master
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 1fefb2b8960e..0f6c10ec56c1 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -150,6 +150,9 @@ static int ovl_mkdir_real(struct inode *dir, struct dentry **newdentry,
 	if (likely(!d_unhashed(dentry)))
 		return 0;
 
+	pr_info("unhashed dentry after mkdir (%s)\n",
+		dentry->d_sb->s_type->name);
+
 	/*
 	 * vfs_mkdir() may succeed and leave the dentry passed
 	 * to it unhashed and negative. If that happens, try to
@@ -209,7 +212,10 @@ struct dentry *ovl_create_real(struct inode *dir, struct dentry *newdentry,
 			err = -EPERM;
 		}
 	}
-	if (!err && WARN_ON(!newdentry->d_inode)) {
+	if (!err && !newdentry->d_inode) {
+		pr_warn("negative dentry after mkdir (%s)\n",
+			newdentry->d_sb->s_type->name);
+		WARN_ON(1);
 		/*
 		 * Not quite sure if non-instantiated dentry is legal or not.
 		 * VFS doesn't seem to care so check and warn here.