linux-kernel - Re: [PATCH] psi: allow unprivileged users with CAP_SYS

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Message-ID: <YGYjbcqThAVOi8kP@cmpxchg.org>
Date:   Thu, 1 Apr 2021 15:47:57 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Josh Hunt <johunt@...mai.com>, Ingo Molnar <mingo@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] psi: allow unprivileged users with CAP_SYS_RESOURCE to
 write psi files

On Thu, Apr 01, 2021 at 08:47:33AM +0200, Peter Zijlstra wrote:
> On Wed, Mar 31, 2021 at 11:31:56PM -0400, Josh Hunt wrote:
> > Currently only root can write files under /proc/pressure. Relax this to
> > allow tasks running as unprivileged users with CAP_SYS_RESOURCE to be
> > able to write to these files.
> > 
> > Signed-off-by: Josh Hunt <johunt@...mai.com>
> 
> I suppose that's ok, but lets also ask Johannes.

The write creates a kthread that runs as SCHED_FIFO. For userspace
threads this is reserved for CAP_SYS_NICE tasks, but it's a kernel
thread and not arbitrary code, so I suppose CAP_SYS_RESOURCE is fine.

Acked-by: Johannes Weiner <hannes@...xchg.org>