linux-kernel - Re: [RFC PATCH] cocci: cpi: add complete api check script

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Date:   Mon, 27 Feb 2023 16:43:59 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Schspa Shi <schspa@...il.com>, linux-kernel@...r.kernel.org,
        cocci@...ia.fr, mcgrof@...nel.org,
        Julia Lawall <Julia.Lawall@...ia.fr>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        buytenh@...tstofly.org, johannes.berg@...el.com,
        gregkh@...uxfoundation.org, tomba@...nel.org, airlied@...il.com,
        daniel@...ll.ch
Subject: Re: [RFC PATCH] cocci: cpi: add complete api check script

On Mon, Feb 27, 2023 at 10:28:08AM -0500, Steven Rostedt wrote:

> So what exact race are you trying to catch here?

on-stack copmletion with a wait_for_completion that can return early
(eg. killable, interruptible, or timeout) can go out of scope (eg, free
the completion) with the other side calling complete() on some possibly
re-used piece of stack.

IOW, Use-after-Free.

Care must be taken to ensure the other side (whatever does complete())
is either terminated or otherwise stopped from calling complete() on an
out-of-scope variable.