1 files changed, 55 insertions, 10 deletions

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index b48273e846ad..7663aeb85fa3 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -1,10 +1,7 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *
  * Copyright (C) 2011 Novell Inc.
- *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 2 as published by
- * the Free Software Foundation.
  */
 
 #include <linux/fs.h>
@@ -553,15 +550,15 @@ static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev,
 	int xinobits = ovl_xino_bits(inode->i_sb);
 
 	/*
-	 * When NFS export is enabled and d_ino is consistent with st_ino
-	 * (samefs or i_ino has enough bits to encode layer), set the same
-	 * value used for d_ino to i_ino, because nfsd readdirplus compares
-	 * d_ino values to i_ino values of child entries. When called from
+	 * When d_ino is consistent with st_ino (samefs or i_ino has enough
+	 * bits to encode layer), set the same value used for st_ino to i_ino,
+	 * so inode number exposed via /proc/locks and a like will be
+	 * consistent with d_ino and st_ino values. An i_ino value inconsistent
+	 * with d_ino also causes nfsd readdirplus to fail.  When called from
 	 * ovl_new_inode(), ino arg is 0, so i_ino will be updated to real
 	 * upper inode i_ino on ovl_inode_init() or ovl_inode_update().
 	 */
-	if (inode->i_sb->s_export_op &&
-	    (ovl_same_sb(inode->i_sb) || xinobits)) {
+	if (ovl_same_sb(inode->i_sb) || xinobits) {
 		inode->i_ino = ino;
 		if (xinobits && fsid && !(ino >> (64 - xinobits)))
 			inode->i_ino |= (unsigned long)fsid << (64 - xinobits);
@@ -777,6 +774,54 @@ struct inode *ovl_lookup_inode(struct super_block *sb, struct dentry *real,
 	return inode;
 }
 
+bool ovl_lookup_trap_inode(struct super_block *sb, struct dentry *dir)
+{
+	struct inode *key = d_inode(dir);
+	struct inode *trap;
+	bool res;
+
+	trap = ilookup5(sb, (unsigned long) key, ovl_inode_test, key);
+	if (!trap)
+		return false;
+
+	res = IS_DEADDIR(trap) && !ovl_inode_upper(trap) &&
+				  !ovl_inode_lower(trap);
+
+	iput(trap);
+	return res;
+}
+
+/*
+ * Create an inode cache entry for layer root dir, that will intentionally
+ * fail ovl_verify_inode(), so any lookup that will find some layer root
+ * will fail.
+ */
+struct inode *ovl_get_trap_inode(struct super_block *sb, struct dentry *dir)
+{
+	struct inode *key = d_inode(dir);
+	struct inode *trap;
+
+	if (!d_is_dir(dir))
+		return ERR_PTR(-ENOTDIR);
+
+	trap = iget5_locked(sb, (unsigned long) key, ovl_inode_test,
+			    ovl_inode_set, key);
+	if (!trap)
+		return ERR_PTR(-ENOMEM);
+
+	if (!(trap->i_state & I_NEW)) {
+		/* Conflicting layer roots? */
+		iput(trap);
+		return ERR_PTR(-ELOOP);
+	}
+
+	trap->i_mode = S_IFDIR;
+	trap->i_flags = S_DEAD;
+	unlock_new_inode(trap);
+
+	return trap;
+}
+
 /*
  * Does overlay inode need to be hashed by lower inode?
  */