linux-kernel - Re: [PATCH v3 3/3] sched_ext: Guarantee rq lock on scx_bpf_cpu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aJebkj-neVJNKEJ4@slm.duckdns.org>
Date: Sat, 9 Aug 2025 09:03:46 -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
Subject: Re: [PATCH v3 3/3] sched_ext: Guarantee rq lock on scx_bpf_cpu_rq()

Hello,

On Tue, Aug 05, 2025 at 12:10:36PM +0100, Christian Loehle wrote:
> @@ -7420,10 +7420,20 @@ __bpf_kfunc s32 scx_bpf_task_cpu(const struct task_struct *p)
>   */
>  __bpf_kfunc struct rq *scx_bpf_cpu_rq(s32 cpu)
>  {
> +	struct rq *rq;
> +
>  	if (!kf_cpu_valid(cpu, NULL))
>  		return NULL;
>  
> -	return cpu_rq(cpu);
> +	preempt_disable();
> +	rq = cpu_rq(cpu);
> +	if (rq != scx_locked_rq()) {
> +		scx_kf_error("Accessing not locked rq %d", cpu);
> +		rq = NULL;
> +	}
> +	preempt_enable();

So, this will break the existing scheduler binaries immediately, which I
don't think is a good way to go about it. Can you add a pr_warn_once() to
print deprecation warning and add e.g. scx_bpf_locked_cpu_rq() instead?

Thanks.

-- 
tejun