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Date: Fri, 22 May 2020 21:27:49 -0700 From: Andrei Vagin <avagin@...il.com> To: Casey Schaufler <casey@...aufler-ca.com> Cc: Adrian Reber <areber@...hat.com>, Christian Brauner <christian.brauner@...ntu.com>, Eric Biederman <ebiederm@...ssion.com>, Pavel Emelyanov <ovzxemul@...il.com>, Oleg Nesterov <oleg@...hat.com>, Dmitry Safonov <0x7f454c46@...il.com>, Nicolas Viennot <Nicolas.Viennot@...sigma.com>, Michał Cłapiński <mclapinski@...gle.com>, Kamil Yurtsever <kyurtsever@...gle.com>, Dirk Petersen <dipeit@...il.com>, Christine Flood <chf@...hat.com>, Mike Rapoport <rppt@...ux.ibm.com>, Radostin Stoyanov <rstoyanov1@...il.com>, Cyrill Gorcunov <gorcunov@...nvz.org>, Serge Hallyn <serge@...lyn.com>, Stephen Smalley <stephen.smalley.work@...il.com>, Sargun Dhillon <sargun@...gun.me>, Arnd Bergmann <arnd@...db.de>, Aaron Goidel <acgoide@...ho.nsa.gov>, linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org, selinux@...r.kernel.org, Eric Paris <eparis@...isplace.org>, Jann Horn <jannh@...gle.com> 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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