linux-kernel - Re: [PATCH 14/16] vfs: Implement mount_super

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 19 Apr 2016 16:29:16 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
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>,
	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>
Subject: Re: [PATCH 14/16] vfs: Implement mount_super_once

On Tue, Apr 19, 2016 at 11:22 AM, Eric W. Biederman
<ebiederm@...ssion.com> wrote:
> Linus Torvalds <torvalds@...ux-foundation.org> writes:
>>
>> No.
>>
>> We want to get *rid* of the idiotic "primary instance" crap.
>
> That is actually pretty much the opposite of what you said last time,
> but having looked at the cost to maintian a "primary instance" notion
> and what will break if we don't I am happy to remove such a notion
> from devpts.

No, it's what I said last time too, but there may have been an misunderstanding.

I _violently_ oppose the stupid DEVPTS_MULTIPLE_INSTANCES config option.

But I do _not_ oppose it because I want to have that "primary
instance" cap. Quite the reverse. I oppose it because the *option* is
stupid, and we should not have such an option.

The kernel should always do multiple instances. There should never
_ever_ be a "single instance" option, although obviously if you were
to do a bind-mount of devpts, the bound mount would be the same
instance.

But if you do two separate mounts, they should alwats be separate insnaces.

So what I want to fix is the crazy "that doesn't work" problem with
Ubuntu or CentOS (or whatever distro it was) breaking, because
/dev/ptmx ends up pointing to the *wrong* instance.

This is literally why I think /dev/ptmx should just look up /dev/pts -
simply to get rid of that idiotic special instance. It should not
exist. It should not exist in the kernel, and it shouldn't exist in
user space.

                 Linus