linux-kernel - Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup

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Message-ID: <87r3ebad6w.fsf@x220.int.ebiederm.org>
Date:	Mon, 11 Apr 2016 19:22:15 -0500
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andy Lutomirski <luto@...capital.net>, security@...ian.org,
	"security\@kernel.org" <security@...nel.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	"security\@ubuntu.com \>\> security" <security@...ntu.com>,
	Peter Hurley <peter@...leysoftware.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>, Greg KH <greg@...ah.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jiri Slaby <jslaby@...e.com>,
	Florian Weimer <fw@...eb.enyo.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup

Linus Torvalds <torvalds@...ux-foundation.org> writes:

> On Mon, Apr 11, 2016 at 4:49 PM, Eric W. Biederman
> <ebiederm@...ssion.com> wrote:
>>
>> I replied earlier.  Did you not see my reply?
>
>
> Are you talking about the one where you agreed that the scenario was
> made up and insane? The one where you said that you're worried about
> breaking out "extension" where ptmx is non-0666?

I meant the one where I conceded that the only think that it could
possible protect against was a denial of service attack, from which we
probably don't care.

I just want to be certain that the emails are getting through.  As the
meaning certainly has not been.

I do think I called a permision check in posix_open aka on /dev/ptmx
a linux specific extension in that email.   But seriously it was all
about reducing the scope of the change.  Reducing the size of the test
matrix.  I simply had not looked far enough to see if there was anything
you could reasonable protect with those permissions.

As I agreed with you that it was unnecessary I was just puzzled why you
called what was essentially agreement with you deafening silence.

Eric