linux-hardening - Re: [PATCH] arm64: smp: smp_send_stop() and crash_smp_send

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Message-ID: <20240624135452.GB8616@willie-the-truck>
Date: Mon, 24 Jun 2024 14:54:52 +0100
From: Will Deacon <will@...nel.org>
To: Doug Anderson <dianders@...omium.org>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Mark Rutland <mark.rutland@....com>, Marc Zyngier <maz@...nel.org>,
	Misono Tomohiro <misono.tomohiro@...itsu.com>,
	Chen-Yu Tsai <wens@...e.org>, Stephen Boyd <swboyd@...omium.org>,
	Daniel Thompson <daniel.thompson@...aro.org>,
	Sumit Garg <sumit.garg@...aro.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	"Guilherme G. Piccoli" <gpiccoli@...lia.com>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Kees Cook <keescook@...omium.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tony Luck <tony.luck@...el.com>,
	Valentin Schneider <vschneid@...hat.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: smp: smp_send_stop() and crash_smp_send_stop()
 should try non-NMI first

On Fri, May 17, 2024 at 01:01:58PM -0700, Doug Anderson wrote:
> On Thu, Dec 7, 2023 at 5:03 PM Douglas Anderson <dianders@...omium.org> wrote:
> >         local_irq_disable();
> 
> The above local_irq_disable() is not new for my patch but it seems
> wonky for two reasons:
> 
> 1. It feels like it should have been the first thing in the function.
> 
> 2. It feels like it should be local_daif_mask() instead.

Is that to ensure we don't take a pNMI? I think that makes sense, but
let's please add a comment to say why local_irq_disable() is not
sufficient.

Will