This is a note to let you know that I've just added the patch titled debugfs: Make automount point inodes permanently empty to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: debugfs-make-automount-point-inodes-permanently-empty.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 87243deb88671f70def4c52dfa7ca7830707bd31 Mon Sep 17 00:00:00 2001 From: Seth Forshee <seth.forshee@xxxxxxxxxxxxx> Date: Wed, 9 Mar 2016 09:18:07 -0600 Subject: debugfs: Make automount point inodes permanently empty From: Seth Forshee <seth.forshee@xxxxxxxxxxxxx> 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 <seth.forshee@xxxxxxxxxxxxx> Acked-by: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/debugfs/inode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/fs/debugfs/inode.c +++ b/fs/debugfs/inode.c @@ -457,7 +457,7 @@ struct dentry *debugfs_create_automount( 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; Patches currently in stable-queue which might be from seth.forshee@xxxxxxxxxxxxx are queue-4.4/debugfs-make-automount-point-inodes-permanently-empty.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html