linux-kernel - Re: [PATCH] sched: core: remove access_ok() before copy_to

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Message-ID: <YvtgyxoZ/RmtfOs/@worktop.programming.kicks-ass.net>
Date:   Tue, 16 Aug 2022 11:18:03 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Tuo Cao <91tuocao@...il.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,
        bristot@...hat.com, vschneid@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: core: remove access_ok() before copy_to_user()

On Mon, Aug 15, 2022 at 10:21:37PM +0800, Tuo Cao wrote:
> If usize > ksize, usize may be not valid and if(!access_ok()) will return
> -EFAULT. But ksize may be valid, copy_to_user() should be executed.And
> also, copy_to_user() will calls access_ok() to test whether a block of
> memory is a valid user space address.

I don't follow, why do you want this to continue if the user provided
garbage input?