3 files changed, 29 insertions, 6 deletions

diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index 73c9775215b3..11dd8177770d 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -482,7 +482,7 @@ static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
 	if (IS_ERR_OR_NULL(this))
 		return this;
 
-	if (WARN_ON(ovl_dentry_real_at(this, layer->idx) != real)) {
+	if (ovl_dentry_real_at(this, layer->idx) != real) {
 		dput(this);
 		this = ERR_PTR(-EIO);
 	}
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 15e4fa288475..7a08a576f7b2 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -21,13 +21,16 @@ static char ovl_whatisit(struct inode *inode, struct inode *realinode)
 		return 'm';
 }
 
+/* No atime modificaton nor notify on underlying */
+#define OVL_OPEN_FLAGS (O_NOATIME | FMODE_NONOTIFY)
+
 static struct file *ovl_open_realfile(const struct file *file,
 				      struct inode *realinode)
 {
 	struct inode *inode = file_inode(file);
 	struct file *realfile;
 	const struct cred *old_cred;
-	int flags = file->f_flags | O_NOATIME | FMODE_NONOTIFY;
+	int flags = file->f_flags | OVL_OPEN_FLAGS;
 
 	old_cred = ovl_override_creds(inode->i_sb);
 	realfile = open_with_fake_path(&file->f_path, flags, realinode,
@@ -48,8 +51,7 @@ static int ovl_change_flags(struct file *file, unsigned int flags)
 	struct inode *inode = file_inode(file);
 	int err;
 
-	/* No atime modificaton on underlying */
-	flags |= O_NOATIME | FMODE_NONOTIFY;
+	flags |= OVL_OPEN_FLAGS;
 
 	/* If some flag changed that cannot be changed then something's amiss */
 	if (WARN_ON((file->f_flags ^ flags) & ~OVL_SETFL_MASK))
@@ -102,7 +104,7 @@ static int ovl_real_fdget_meta(const struct file *file, struct fd *real,
 	}
 
 	/* Did the flags change since open? */
-	if (unlikely((file->f_flags ^ real->file->f_flags) & ~O_NOATIME))
+	if (unlikely((file->f_flags ^ real->file->f_flags) & ~OVL_OPEN_FLAGS))
 		return ovl_change_flags(real->file, file->f_flags);
 
 	return 0;
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 7621ff176d15..d6b724beb304 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1258,6 +1258,18 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
 	if (!ofs->config.nfs_export && !ofs->upper_mnt)
 		return true;
 
+	/*
+	 * We allow using single lower with null uuid for index and nfs_export
+	 * for example to support those features with single lower squashfs.
+	 * To avoid regressions in setups of overlay with re-formatted lower
+	 * squashfs, do not allow decoding origin with lower null uuid unless
+	 * user opted-in to one of the new features that require following the
+	 * lower inode of non-dir upper.
+	 */
+	if (!ofs->config.index && !ofs->config.metacopy && !ofs->config.xino &&
+	    uuid_is_null(uuid))
+		return false;
+
 	for (i = 0; i < ofs->numlowerfs; i++) {
 		/*
 		 * We use uuid to associate an overlay lower file handle with a
@@ -1344,14 +1356,23 @@ static int ovl_get_lower_layers(struct super_block *sb, struct ovl_fs *ofs,
 		if (err < 0)
 			goto out;
 
+		/*
+		 * Check if lower root conflicts with this overlay layers before
+		 * checking if it is in-use as upperdir/workdir of "another"
+		 * mount, because we do not bother to check in ovl_is_inuse() if
+		 * the upperdir/workdir is in fact in-use by our
+		 * upperdir/workdir.
+		 */
 		err = ovl_setup_trap(sb, stack[i].dentry, &trap, "lowerdir");
 		if (err)
 			goto out;
 
 		if (ovl_is_inuse(stack[i].dentry)) {
 			err = ovl_report_in_use(ofs, "lowerdir");
-			if (err)
+			if (err) {
+				iput(trap);
 				goto out;
+			}
 		}
 
 		mnt = clone_private_mount(&stack[i]);