linux-kernel - Re: [PATCH v7 0/3] sched_ext: Harden scx_bpf_cpu

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Message-ID: <aLi4tSqsdF-CpF2R@slm.duckdns.org>
Date: Wed, 3 Sep 2025 11:52:53 -1000
From: Tejun Heo <tj@...nel.org>
To: Christian Loehle <christian.loehle@....com>
Cc: arighi@...dia.com, void@...ifault.com, linux-kernel@...r.kernel.org,
	sched-ext@...ts.linux.dev, changwoo@...lia.com, hodgesd@...a.com,
	mingo@...hat.com, peterz@...radead.org, jake@...lion.co.uk
Subject: Re: [PATCH v7 0/3] sched_ext: Harden scx_bpf_cpu_rq()

On Wed, Sep 03, 2025 at 10:23:08PM +0100, Christian Loehle wrote:
> scx_bpf_cpu_rq() currently allows accessing struct rq fields without
> holding the associated rq.
> It is being used by scx_cosmos, scx_flash, scx_lavd, scx_layered, and
> scx_tickless. Fortunately it is only ever used to fetch rq->curr.
> So provide an alternative scx_bpf_cpu_curr() that doesn't expose struct rq
> and provide a hardened scx_bpf_locked_rq() by ensuring we hold the rq lock.
> Add a deprecation warning to scx_bpf_cpu_rq() that mentions the two alternatives.
> 
> This also simplifies scx code from:
> 
> rq = scx_bpf_cpu_rq(cpu);
> if (!rq)
> 	return;
> p = rq->curr
> /* ... Do something with p */
> 
> into:
> 
> p = scx_bpf_cpu_curr(cpu);
> /* ... Do something with p */

Applied 1-3 to sched_ext/for-6.18 (the last patch needed a bit of update to
account for struct scx_sched defintion being moved to ext_internal.h).

Thanks.

-- 
tejun