linux-kernel - Re: [PATCH v6 0/1] ns: introduce binfmt

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Date:   Thu, 01 Nov 2018 09:16:04 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Laurent Vivier <laurent@...ier.eu>
Cc:     Jann Horn <jannh@...gle.com>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        kernel list <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        containers@...ts.linux-foundation.org, dima@...sta.com,
        Al Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v6 0/1] ns: introduce binfmt_misc namespace

Laurent Vivier <laurent@...ier.eu> writes:

> On 01/11/2018 04:51, Jann Horn wrote:
>> On Thu, Nov 1, 2018 at 3:59 AM James Bottomley
>> <James.Bottomley@...senpartnership.com> wrote:
>>>
>>> On Tue, 2018-10-16 at 11:52 +0200, Laurent Vivier wrote:
>>>> Hi,
>>>>
>>>> Any comment on this last version?
>>>>
>>>> Any chance to be merged?
>>>
>>> I've got a use case for this:  I went to one of the Graphene talks in
>>> Edinburgh and it struck me that we seem to keep reinventing the type of
>>> sandboxing that qemu-user already does.  However if you want to do an
>>> x86 on x86 sandbox, you can't currently use the binfmt_misc mechanism
>>> because that has you running *every* binary on the system emulated.
>>> Doing it per user namespace fixes this problem and allows us to at
>>> least cut down on all the pointless duplication.
>> 
>> Waaaaaait. What? qemu-user does not do "sandboxing". qemu-user makes
>> your code slower and *LESS* secure. As far as I know, qemu-user is
>> only intended for purposes like development and testing.
>> 
>
> I think the idea here is not to run qemu, but to use an interpreter
> (something like gVisor) into a container to control the binaries
> execution inside the container without using this interpreter on the
> host itself (container and host shares the same binfmt_misc
> magic/mask).

Please remind me of this patchset after the merge window is over, and if
there are no issues I will take it via my user namespace branch.

Last I looked I had a concern that some of the permission check issues
were being papered over by using override cred instead of fixing the
deaper code.  Sometimes they are necessary but seeing work-arounds
instead of fixes for problems tends to be a maintenance issue, possibly
with security consequences.  Best is if the everyone agrees on how all
of the interfaces work so their are no surprises.

Eric