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From: Andrei Vagin <avagin@gmail.com>
To: Christian Brauner <christian.brauner@ubuntu.com>
Cc: "Adrian Reber" <areber@redhat.com>,
	"Eric Biederman" <ebiederm@xmission.com>,
	"Pavel Emelyanov" <ovzxemul@gmail.com>,
	"Oleg Nesterov" <oleg@redhat.com>,
	"Dmitry Safonov" <0x7f454c46@gmail.com>,
	"Nicolas Viennot" <Nicolas.Viennot@twosigma.com>,
	"Michał Cłapiński" <mclapinski@google.com>,
	"Kamil Yurtsever" <kyurtsever@google.com>,
	"Dirk Petersen" <dipeit@gmail.com>,
	"Christine Flood" <chf@redhat.com>,
	"Mike Rapoport" <rppt@linux.ibm.com>,
	"Radostin Stoyanov" <rstoyanov1@gmail.com>,
	"Cyrill Gorcunov" <gorcunov@openvz.org>,
	"Serge Hallyn" <serge@hallyn.com>,
	"Stephen Smalley" <stephen.smalley.work@gmail.com>,
	"Sargun Dhillon" <sargun@sargun.me>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Aaron Goidel" <acgoide@tycho.nsa.gov>,
	linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org, selinux@vger.kernel.org,
	"Eric Paris" <eparis@parisplace.org>,
	"Jann Horn" <jannh@google.com>
Subject: Re: [PATCH] capabilities: Introduce CAP_RESTORE
Date: Fri, 22 May 2020 11:02:28 -0700
Message-ID: <20200522180228.GA6466@gmail.com> (raw)
In-Reply-To: <20200522075331.ef7zcz3hbke7qvem@wittgenstein>

On Fri, May 22, 2020 at 09:53:31AM +0200, Christian Brauner wrote:
> On Fri, May 22, 2020 at 07:53:50AM +0200, Adrian Reber wrote:
> > 
> > There are probably a few more things guarded by CAP_SYS_ADMIN required
> > to run checkpoint/restore as non-root, 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.
> 
> It sounds ok to me as long as this feature is guarded by any sensible
> capability. I don't want users to be able to randomly choose their pid
> without any capability required.
> 
> We've heard the plea for unprivileged checkpoint/restore through the
> grapevine and a few times about CAP_RESTORE at plumbers but it's one of
> those cases where nobody pushed for it so it's urgency was questionable.
> This is 5.9 material though and could you please add selftests?
> 
> It also seems you have future changes planned that would make certain
> things accessible via CAP_RESTORE that are currently guarded by other
> capabilities. Any specific things in mind? It might be worth knowing
> what we'd be getting ourselves into if you're planning on flipping
> switches in other places.

/proc/pid/map_files is one of the first candidate what we need to think
about. CRIU opens files from /proc/pid/map_files to dump file mappings,
shared memory mappings, memfd files.

Right now, it is impossible to open these files without CAP_SYS_ADMIN in
the root user-namespace (proc_map_files_get_link).

  reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-22  5:53 Adrian Reber
2020-05-22  7:53 ` Christian Brauner
2020-05-22 18:02   ` Andrei Vagin [this message]
2020-05-22 13:41 ` Christian Brauner
2020-05-22 16:40 ` Casey Schaufler
2020-05-23  4:27   ` Andrei Vagin
2020-05-25  2:01     ` Casey Schaufler
2020-05-25  8:05   ` Adrian Reber
2020-05-25 18:55     ` Casey Schaufler
2020-05-27 13:48       ` Adrian Reber
2020-05-27 15:57         ` Casey Schaufler
2020-05-27 16:37           ` Nicolas Viennot
2020-05-27 16:46             ` Casey Schaufler
2020-05-26 13:59     ` Eric W. Biederman
     [not found]       ` <CALKUemw0UZ67yaDwAomHh0n8QZfjd52QvgEXTJ4R3JSrQjZX9g@mail.gmail.com>
2020-05-26 19:19         ` Casey Schaufler
2020-05-26 19:51         ` Jann Horn
2020-05-27 14:14       ` Adrian Reber
2020-05-27 15:29         ` Christian Brauner
2020-05-27 18:05           ` Nicolas Viennot
2020-05-28  9:48             ` Christian Brauner
2020-05-25 21:53 ` Jann Horn
2020-05-26  9:09   ` Radostin Stoyanov

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