linux-kernel - Re: [PATCH 0/1] devpts: Removing the need for pt

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Date:	Fri, 6 May 2016 12:45:01 -0700
From:	Peter Hurley <peter@...leysoftware.com>
To:	Greg KH <greg@...ah.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>, security@...ian.org,
	"security@...nel.org" <security@...nel.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	"security@...ntu.com >> security" <security@...ntu.com>,
	Serge Hallyn <serge.hallyn@...ntu.com>,
	Willy Tarreau <w@....eu>,
	Aurelien Jarno <aurelien@...el32.net>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Jann Horn <jann@...jh.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jiri Slaby <jslaby@...e.com>,
	Florian Weimer <fw@...eb.enyo.de>,
	Konstantin Khlebnikov <koct9i@...il.com>
Subject: Re: [PATCH 0/1] devpts: Removing the need for pt_chown

On 05/06/2016 12:35 PM, Greg KH wrote:
> On Fri, May 06, 2016 at 02:04:12PM -0500, Eric W. Biederman wrote:
>>
>> Greg,
>>
>> Could you please apply the following patch to tty-next so it can be
>> merged into 4.7-rc1.
>>
>> We have had a long series of discussions and in the last iteration we
>> finally converged on a set of semantics that does not break userspace
>> and also makes the code simpler.
> 
> Did everyone agree?  I didn't think so, but the thread got long and
> messy.  And then Linus did some work on this as well.
> 
> How does this play with what Linus proposed?  I think only portions of
> his original changes are merged, and there are still outstanding parts,
> right?

Linus committed his proposed pty changes which sits in -rc6 and not
in tty-next (which is based on -rc5):

commit 8ead9dd54716d1e05e129959f702fcc1786f82b4
Author: Linus Torvalds <torvalds@...ux-foundation.org>
Date:   Mon Apr 25 20:04:08 2016 -0700

    devpts: more pty driver interface cleanups
    
    This is more prep-work for the upcoming pty changes.  Still just code
    cleanup with no actual semantic changes.
    
    This removes a bunch pointless complexity by just having the slave pty
    side remember the dentry associated with the devpts slave rather than
    the inode.  That allows us to remove all the "look up the dentry" code
    for when we want to remove it again.

    ....


Linus's changes look good to me and I've been running them cherry-picked on
my private tty-next testing tree since.

When Greg picks up -rc6 (not sure he was going to do that pre-merge window?),
I'd also like to push the devpts_mutex locking down into fs/devpts/inode.c,
but I'd be willing to do that later, if it's going to get in the way.

Regards,
Peter Hurley