linux-kernel - Re: [kernel-hardening] Re: [PATCH resend 2/2] userns: control capabilities of some user namespaces

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Message-ID: <CAF2d9jjLbN6TLZ2H888zku4Xupsqr-X66d7QCvtXsCzkyNFoDQ@mail.gmail.com>
Date:   Fri, 10 Nov 2017 14:28:04 +0900
From:   Mahesh Bandewar (महेश बंडेवार) 
        <maheshb@...gle.com>
To:     "Serge E. Hallyn" <serge@...lyn.com>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Christian Brauner <christian.brauner@...onical.com>,
        Boris Lukashev <blukashev@...pervictus.com>,
        Daniel Micay <danielmicay@...il.com>,
        Mahesh Bandewar <mahesh@...dewar.net>,
        LKML <linux-kernel@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>,
        Kernel-hardening <kernel-hardening@...ts.openwall.com>,
        Linux API <linux-api@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        Eric Dumazet <edumazet@...gle.com>,
        David Miller <davem@...emloft.net>
Subject: Re: [kernel-hardening] Re: [PATCH resend 2/2] userns: control
 capabilities of some user namespaces

On Fri, Nov 10, 2017 at 1:46 PM, Serge E. Hallyn <serge@...lyn.com> wrote:
> Quoting Eric W. Biederman (ebiederm@...ssion.com):
>> single sandbox.  I am not at all certain that the capabilities is the
>> proper place to limit code reachability.
>
> Right, I keep having this gut feeling that there is another way we
> should be doing that.  Maybe based on ksplice or perf, or maybe more
> based on subsystems.  And I hope someone pursues that.  But I can't put
> my finger on it, and meanwhile the capability checks obviously *are* in
> fact gates...
>
Well, I don't mind if there is a better solution available. The
proposed solution is not adding too much or complex code and using a
bit and a sysctl and will be sitting dormant. When we have complete
solution, this addition should not be a burden to maintain because of
it's non-invasive footprint.

I will push the next version of the patch-set that implements Serge's finding.

Thanks,
--mahesh..

[PS: I'll be soon traveling again and moving to an area where
connectivity will be scarce / unreliable. So please expect lot more
delays in my responses.]

> -serge