Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753480AbcDZSgI (ORCPT ); Tue, 26 Apr 2016 14:36:08 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:56378 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752902AbcDZSSf (ORCPT ); Tue, 26 Apr 2016 14:18:35 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Seth Forshee , Greg Kroah-Hartman , Kamal Mostafa Subject: [PATCH 4.2.y-ckt 40/93] debugfs: Make automount point inodes permanently empty Date: Tue, 26 Apr 2016 11:16:40 -0700 Message-Id: <1461694653-29506-41-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1461694653-29506-1-git-send-email-kamal@canonical.com> References: <1461694653-29506-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 4.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1959 Lines: 50 4.2.8-ckt9 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Seth Forshee commit 87243deb88671f70def4c52dfa7ca7830707bd31 upstream. 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. Signed-off-by: Seth Forshee Acked-by: Serge Hallyn Signed-off-by: Greg Kroah-Hartman Signed-off-by: Kamal Mostafa --- 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 9c8d233..6d0ead7 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; -- 2.7.4