From: ebiederm@xmission.com (Eric W. Biederman)
To: Stefan Lippers-Hollmann <s.l-h@gmx.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Christian Brauner <christian.brauner@canonical.com>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Thorsten Leemhuis <regressions@leemhuis.info>
References: <20170816171211.4021-1-christian.brauner@ubuntu.com>
        <20170816194805.hnof3aqiqykwki7p@gmail.com>
        <CA+55aFzmcydKsuwXpocd0hYMrACEXt+UUuaqa7j3L5LG7SjajQ@mail.gmail.com>
        <CA+55aFxMnEQVq8zRG1JEsW+6x23qkBV=KKXksgVHmBegPuepMg@mail.gmail.com>
        <CA+55aFz+qGxM9MidcvQkP4er-qn0_oEqCac=ob64f+twhptSgQ@mail.gmail.com>
        <CA+55aFxXzwoDdN72m2oaV4XuxO0DGoT+Bp84i07VFpLQ3Ftcpw@mail.gmail.com>
        <87pobvruzt.fsf@xmission.com>
        <CA+55aFyJsxsxeW-8RX83AM2zs+_i8h85i99X+YkuFEqpqjtp4w@mail.gmail.com>
        <87ziazqdfr.fsf@xmission.com>
        <CA+55aFwssaZpapQdc2iVVmMt0KxTHYdeo71Xbp4Ex-pYP_MpMw@mail.gmail.com>
        <20170824022436.44adb497@mir>
        <CA+55aFzHa0vL2Yui05r6aSQM0-oHuUAjqi1kxheG_tFQRkUGYw@mail.gmail.com>
        <87378hhi3y.fsf@xmission.com>
        <CA+55aFxhg8=KMZDtF-TrVjb3fPNvSWUveuRy1HHGuWXQ3+YzwQ@mail.gmail.com>
        <CA+55aFw737C9OVC2nQgGcazhi7Ca2K-frzgN2MiD=XqqFAp8YA@mail.gmail.com>
        <CA+55aFwvwtFCH2THn1LirOpMsZ57pnNi61nXQfQ6NBgakdXpTQ@mail.gmail.com>
        <87wp5tfynr.fsf@xmission.com> <20170824062432.1e05e6f8@mir>
Date: Thu, 24 Aug 2017 10:54:58 -0500
In-Reply-To: <20170824062432.1e05e6f8@mir> (Stefan Lippers-Hollmann's message
        of "Thu, 24 Aug 2017 06:24:32 +0200")
Message-ID: <874lsxezal.fsf@xmission.com>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain
Subject: Re: [PATCH 0/1] devpts: use dynamic_dname() to generate proc name
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1519
Lines: 38

Stefan Lippers-Hollmann <s.l-h@gmx.de> writes:

> Hi
>
> On 2017-08-23, Eric W. Biederman wrote:
>> Linus Torvalds <torvalds@linux-foundation.org> writes:
>> > On Wed, Aug 23, 2017 at 6:49 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote:  
> [...]
>> This is so far untested (except for compiling) but I think this will
>> work.
>> 
>> I factor out devpts_ptmx_path out of devpts_acquire so the code
>> doesn't have to do unnecessary and confusing work, and add the
>> new function devpts_mnt.
>> 
>> I revert the code to keep anything except a dentry in
>> tty->link->driver_data.
>> 
>> And reduce the peer opening to a single function ptm_open_peer.
>> 
>> It takes lines of code but the result is very straightforward code.
>
> I've given this a quick test, while it seems to fix the initial problem
> with umounting /dev/ptmx, it does introduce a new one - trying to open 
> an xterm (KDE5's konsole to be exact) doesn't open a shell (the shell 
> window remains totally empty) and trying to ssh into the system fails 
> with "PTY allocation request failed on channel 0", logging in via a 
> real tty and creating a new pbuilder chroot from there succeeds.

Weird.  There is at least one leak inducing bug in there.  So perhaps
that is the cause.   *Scratches my head*  Are you also testing the new
ioctl?

I will resend shortly with a version that has no differences in the old
code from v4.12 (other than the refactoring in fs/devpts/inode.c).
Which should make it very hard to have a regression.

Eric