Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933041AbcCIPSc (ORCPT ); Wed, 9 Mar 2016 10:18:32 -0500 Received: from mail-ob0-f173.google.com ([209.85.214.173]:35449 "EHLO mail-ob0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932928AbcCIPSS (ORCPT ); Wed, 9 Mar 2016 10:18:18 -0500 From: Seth Forshee To: "Eric W. Biederman" , Greg Kroah-Hartman Cc: "Serge E. Hallyn" , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Seth Forshee Subject: [PATCH 2/2] debugfs: Make automount point inodes permanently empty Date: Wed, 9 Mar 2016 09:18:07 -0600 Message-Id: <1457536687-32794-3-git-send-email-seth.forshee@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1457536687-32794-1-git-send-email-seth.forshee@canonical.com> References: <1457536687-32794-1-git-send-email-seth.forshee@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1578 Lines: 40 Starting with 4.1 the tracing subsystem has its own filesystem which is automounted in the tracing subdirectory of debugfs. Prior to this debugfs could be bind mounted in a cloned mount namespace, but if tracefs has been mounted under debugfs this now fails because there is a locked child mount. This creates a regression for container software which bind mounts debugfs to satisfy the assumption of some userspace software. In other pseudo filesystems such as proc and sysfs we're already creating mountpoints like this in such a way that no dirents can be created in the directories, allowing them to be exceptions to some MNT_LOCKED tests. In fact we're already do this for the tracefs mountpoint in sysfs. Do the same in debugfs_create_automount(), since the intention here is clearly to create a mountpoint. This fixes the regression, as locked child mounts on permanently empty directories do not cause a bind mount to fail. Cc: stable@vger.kernel.org # v4.1+ Signed-off-by: Seth Forshee --- fs/debugfs/inode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c index bece948b363d..8580831ed237 100644 --- a/fs/debugfs/inode.c +++ b/fs/debugfs/inode.c @@ -457,7 +457,7 @@ struct dentry *debugfs_create_automount(const char *name, if (unlikely(!inode)) return failed_creating(dentry); - inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO; + make_empty_dir_inode(inode); inode->i_flags |= S_AUTOMOUNT; inode->i_private = data; dentry->d_fsdata = (void *)f; -- 1.9.1