linux-hardening - Re: [PATCH] Revert "ACPI, APEI, use raw spinlock in ERST"

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Message-ID: <ZOV1sM8xZ6+P48Z1@cork>
Date:   Tue, 22 Aug 2023 19:57:52 -0700
From:   Jörn Engel <joern@...estorage.com>
To:     "Huang, Ying" <ying.huang@...el.com>
Cc:     Uday Shankar <ushankar@...estorage.com>,
        Kees Cook <keescook@...omium.org>,
        Tony Luck <tony.luck@...el.com>,
        "Guilherme G. Piccoli" <gpiccoli@...lia.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>, James Morse <james.morse@....com>,
        Borislav Petkov <bp@...en8.de>,
        Len Brown <len.brown@...el.com>,
        linux-hardening@...r.kernel.org, linux-acpi@...r.kernel.org,
        Qiuxu Zhuo <qiuxu.zhuo@...el.com>
Subject: Re: [PATCH] Revert "ACPI, APEI, use raw spinlock in ERST"

On Wed, Aug 23, 2023 at 10:38:23AM +0800, Huang, Ying wrote:
> 
> Thanks for reminding!  That's a good point.
> 
> Checked the implementation of rt_mutex version of spin_trylock().  One
> possible code path is,
> 
> spin_trylock()
>   rt_spin_trylock()
>     __rt_spin_trylock()
>       rt_mutex_slowtrylock()
>         raw_spin_lock_irqsave()

You are right.  I'm actually quite surprised how we turn a trylock into
a spinning lock.  Now I know, thank you!

Jörn

--
"Security vulnerabilities are here to stay."
-- Scott Culp, Manager of the Microsoft Security Response Center, 2001