linux-kernel - Re: [PATCH -next 2/2] cgroup: Disallow delegatee to write all interfaces outsize of cgroup ns

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Message-ID: <ZrutqDox2rrr7dlA@slm.duckdns.org>
Date: Tue, 13 Aug 2024 09:02:00 -1000
From: Tejun Heo <tj@...nel.org>
To: Michal Koutný <mkoutny@...e.com>
Cc: Chen Ridong <chenridong@...wei.com>, lizefan.x@...edance.com,
	hannes@...xchg.org, longman@...hat.com, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next 2/2] cgroup: Disallow delegatee to write all
 interfaces outsize of cgroup ns

Hello,

On Mon, Aug 12, 2024 at 06:57:06PM +0200, Michal Koutný wrote:
...
> You could also have increased the ancestral limit (if there was any)
> echo max > dlgt_grp_ns/pids.max // similarly allowed
> 
> If you're a root (or otherwise have sufficient permissions) and you can
> _see_ an ancestral cgroup, you can write to its attributes according to
> permissions. Thus the delegation works via cgroup ns (in)visibility but
> cgroup ns root is visible on both sides of the boundary hence the extra
> check.

Yeah, the intended usage scenario w/ NS delegation is that the delegatee
won't be able to see the ancetral cgroups beyond the delegation point. Chen,
is this from an actual usecase? If so, can you describe what's going on?

Thanks.

-- 
tejun