[RFC][PATCH] ovl_create_index(): vfs_mkdir() might succeed leaving dentry negative unhashed

[Al Viro <viro@xxxxxxxxxxxxxxxxxx>]

[same story as with the previous two patches]

Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 8bede0742619..cdd8f8816d2a 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -373,6 +373,22 @@ static int ovl_create_index(struct dentry *dentry, struct dentry *origin,
 	if (err)
 		goto out;
 
+	if (unlikely(d_unhashed(temp))) {
+		struct dentry *d = lookup_one_len(temp->d_name.name,
+						  temp->d_parent,
+						  temp->d_name.len);
+		if (IS_ERR(d)) {
+			err = PTR_ERR(d);
+			goto out;
+		}
+		dput(temp);
+		temp = d;
+		if (d_is_negative(temp)) {
+			err = -EIO;
+			goto out;
+		}
+	}
+
 	err = ovl_set_upper_fh(upper, temp);
 	if (err)
 		goto out_cleanup;