linux-kernel - Re: [PATCH AUTOSEL 6.4 01/15] cpu/hotplug: Reset task stack state in _cpu

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Message-ID: <77ce6f91f163f333d4b2146e6ea66b7f5fe38d9e.camel@infradead.org>
Date:   Mon, 03 Jul 2023 10:17:48 +0100
From:   David Woodhouse <dwmw2@...radead.org>
To:     Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Oleksandr Natalenko <oleksandr@...alenko.name>,
        Helge Deller <deller@....de>,
        "Guilherme G . Piccoli" <gpiccoli@...lia.com>
Subject: Re: [PATCH AUTOSEL 6.4 01/15] cpu/hotplug: Reset task stack state
 in _cpu_up()

On Sun, 2023-07-02 at 15:40 -0400, Sasha Levin wrote:
> From: David Woodhouse <dwmw@...zon.co.uk>
> 
> [ Upstream commit 6d712b9b3a58018259fb40ddd498d1f7dfa1f4ec ]
> 
> Commit dce1ca0525bf ("sched/scs: Reset task stack state in bringup_cpu()")
> ensured that the shadow call stack and KASAN poisoning were removed from
> a CPU's stack each time that CPU is brought up, not just once.
> 
> This is not incorrect.

No really, it *wasn't* incorrect. This isn't a bugfix that needs
backporting; it's preparation for the parallel CPU bringup which I
*hope* you aren't planning to backport in its entirety :)

Unless I'm missing something, I don't think you want this for stable
(in any of the trees it was just sent out for).



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