linux-kernel - Re: PATCH? fix unshare(NEWPID) && vfork()

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Message-ID: <CALCETrU4gTfzcpeEo-X7o-yZefKiw9BVNKdcN4fThUeiuZtOOg@mail.gmail.com>
Date:	Tue, 20 Aug 2013 10:59:10 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Brad Spengler <spender@...ecurity.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Colin Walters <walters@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: PATCH? fix unshare(NEWPID) && vfork()

On Mon, Aug 19, 2013 at 11:43 AM, Oleg Nesterov <oleg@...hat.com> wrote:
> On 08/19, Andy Lutomirski wrote:
>>
>> On Mon, Aug 19, 2013 at 11:33 AM, Oleg Nesterov <oleg@...hat.com> wrote:
>> >
>> > So do you think this change is fine or not (ignoring the fact it needs
>> > cleanups) ?
>>
>> I think that removing the CLONE_VM check is fine (although there are
>> some other ones that should probably be removed as well), but I'm not
>> sure if that check needs replacing with something else.
>
> OK, thanks... but I still can't understand.
>
> The patch I sent is equivalent to the new one below. I just tried to
> unify it with another check in do_fork().

I was confused.

Currently (with or without your patch), vfork() followed by
unshare(CLONE_NEWUSER) or unshare(CLONE_NEWPID) will unshare the VM.
This may be surprising, but at least it will work.

--Andy
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