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From: Tejun Heo <tj@kernel.org>
To: "Michal Koutný" <mkoutny@suse.com>
Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
	Zefan Li <lizefan.x@bytedance.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Waiman Long <longman@redhat.com>
Subject: Re: [RFC PATCH] cpuset: Allow setscheduler regardless of manipulated task
Date: Sat, 25 Jun 2022 13:20:30 +0900	[thread overview]
Message-ID: <YraNDoxU9IZaP3RV@mtj.duckdns.org> (raw)
In-Reply-To: <20220623124944.2753-1-mkoutny@suse.com>

Hello,

On Thu, Jun 23, 2022 at 02:49:44PM +0200, Michal Koutný wrote:
> 1) The unified hierarchy attachment behavior -- is that the
>    right/consented model that migrated objects don't matter?

Yes.

> 2) If 1) is true, have I missed any danger in allowing cpuset'ing a
>    possibly privileged processes?

Given that the someone who has write perm on the cgroup or its
ancestors are allowed to change cpuset config itself, I have a hard
time imagining that check being all that useful as a security
mechanism.

> 2.2) cpuset may be in v2 mode even on v1 hierarchy with different
>    migration control rules (but checking migratee's creds in v1
>    eliminates effect of this patch).

Yeah, it should be fine to apply the change only to v2.

> 3) Alternative approach would be to allow cpuset migrations only when
>    nothing effectively changes (which is the case for parent->child
>    migration upon controller enablement).
> 
> 4) This is just idea draft, not tested in the real case.

Unless I'm missing something obvious, I don't see a reason to keep the
check, so please feel free to test and send a SOB'd patch.

Thanks.

-- 
tejun

WARNING: multiple messages have this Message-ID (diff)
From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: "Michal Koutný" <mkoutny-IBi9RG/b67k@public.gmane.org>
Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Zefan Li <lizefan.x-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org>,
	Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
	Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: [RFC PATCH] cpuset: Allow setscheduler regardless of manipulated task
Date: Sat, 25 Jun 2022 13:20:30 +0900	[thread overview]
Message-ID: <YraNDoxU9IZaP3RV@mtj.duckdns.org> (raw)
In-Reply-To: <20220623124944.2753-1-mkoutny-IBi9RG/b67k@public.gmane.org>

Hello,

On Thu, Jun 23, 2022 at 02:49:44PM +0200, Michal Koutný wrote:
> 1) The unified hierarchy attachment behavior -- is that the
>    right/consented model that migrated objects don't matter?

Yes.

> 2) If 1) is true, have I missed any danger in allowing cpuset'ing a
>    possibly privileged processes?

Given that the someone who has write perm on the cgroup or its
ancestors are allowed to change cpuset config itself, I have a hard
time imagining that check being all that useful as a security
mechanism.

> 2.2) cpuset may be in v2 mode even on v1 hierarchy with different
>    migration control rules (but checking migratee's creds in v1
>    eliminates effect of this patch).

Yeah, it should be fine to apply the change only to v2.

> 3) Alternative approach would be to allow cpuset migrations only when
>    nothing effectively changes (which is the case for parent->child
>    migration upon controller enablement).
> 
> 4) This is just idea draft, not tested in the real case.

Unless I'm missing something obvious, I don't see a reason to keep the
check, so please feel free to test and send a SOB'd patch.

Thanks.

-- 
tejun

  parent reply	other threads:[~2022-06-25  4:20 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-23 12:49 [RFC PATCH] cpuset: Allow setscheduler regardless of manipulated task Michal Koutný
2022-06-23 12:49 ` Michal Koutný
2022-06-23 18:44 ` Waiman Long
2022-06-23 18:44   ` Waiman Long
2022-06-24 12:43   ` Michal Koutný
2022-06-24 12:43     ` Michal Koutný
2022-06-25  4:20 ` Tejun Heo [this message]
2022-06-25  4:20   ` Tejun Heo

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