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Date:   Fri, 22 May 2020 21:27:49 -0700
From:   Andrei Vagin <>
To:     Casey Schaufler <>
Cc:     Adrian Reber <>,
        Christian Brauner <>,
        Eric Biederman <>,
        Pavel Emelyanov <>,
        Oleg Nesterov <>,
        Dmitry Safonov <>,
        Nicolas Viennot <>,
        Michał Cłapiński <>,
        Kamil Yurtsever <>,
        Dirk Petersen <>,
        Christine Flood <>,
        Mike Rapoport <>,
        Radostin Stoyanov <>,
        Cyrill Gorcunov <>,
        Serge Hallyn <>,
        Stephen Smalley <>,
        Sargun Dhillon <>,
        Arnd Bergmann <>,
        Aaron Goidel <>,,,,
        Eric Paris <>,
        Jann Horn <>
Subject: Re: [PATCH] capabilities: Introduce CAP_RESTORE

On Fri, May 22, 2020 at 09:40:37AM -0700, Casey Schaufler wrote:
> On 5/21/2020 10:53 PM, Adrian Reber wrote:
> > There are probably a few more things guarded by CAP_SYS_ADMIN required
> > to run checkpoint/restore as non-root,
> If you need CAP_SYS_ADMIN anyway you're not gaining anything by
> separating out CAP_RESTORE.
> >  but by applying this patch I can
> > already checkpoint and restore processes as non-root. As there are
> > already multiple workarounds I would prefer to do it correctly in the
> > kernel to avoid that CRIU users are starting to invent more workarounds.
> You've presented a couple of really inappropriate implementations
> that would qualify as workarounds. But the other two are completely
> appropriate within the system security policy. They don't "get around"
> the problem, they use existing mechanisms as they are intended.

With CAP_CHECKPOINT_RESTORE, we will need to use the same mechanisms.

The problem is that CAP_SYS_ADMIN is too wide. If a process has
CAP_SYS_ADMIN, it can do a lot of things and  the operation of forking a
process with a specified pid isn't the most dangerous one in this case.
Offten security policies don't allow to grant CAP_SYS_ADMIN to any
third-party tools even in non-root user namespaces.

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