linux-kernel - Re: [PATCH] sched/fair: Fix overflow in vruntime

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Message-ID: <20250710111334.GD542000@noisy.programming.kicks-ass.net>
Date: Thu, 10 Jul 2025 13:13:34 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Zicheng Qu <quzicheng@...wei.com>
Cc: mingo@...hat.com, juri.lelli@...hat.com, vincent.guittot@...aro.org,
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
	mgorman@...e.de, vschneid@...hat.com, linux-kernel@...r.kernel.org,
	tanghui20@...wei.com, zhangqiao22@...wei.com,
	judy.chenhui@...wei.com
Subject: Re: [PATCH] sched/fair: Fix overflow in vruntime_eligible() causing
 NULL return

On Thu, Jul 10, 2025 at 10:01:15AM +0800, Zicheng Qu wrote:
> Hi,
> 
> Based on LTS 6.6. I also looked at the code logic around vruntime_eligible()
> in the mainline. It seems that if vruntime_eligible() consistently returned
> false, this could lead to null pointer dereferences.

That is a truly ancient kernel.  Please verify the issue is reproducible
on something recent.

Specifically, commit bbce3de72be5 ("sched/eevdf: Fix se->slice being set
to U64_MAX and resulting crash") cured something very similar to this.