linux-kernel - Re: [PATCH v2] serial: kgdboc: Fix NMI-safety problems from keyboard reset code

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Message-ID: <2024042427-luster-unbend-5ed6@gregkh>
Date: Wed, 24 Apr 2024 14:23:42 -0700
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Daniel Thompson <daniel.thompson@...aro.org>
Cc: Jason Wessel <jason.wessel@...driver.com>,
	Douglas Anderson <dianders@...omium.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	kgdb-bugreport@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org, Liuye <liu.yeC@....com>,
	stable@...r.kernel.org
Subject: Re: [PATCH v2] serial: kgdboc: Fix NMI-safety problems from keyboard
 reset code

On Wed, Apr 24, 2024 at 03:21:41PM +0100, Daniel Thompson wrote:
> Currently, when kdb is compiled with keyboard support, then we will use
> schedule_work() to provoke reset of the keyboard status.  Unfortunately
> schedule_work() gets called from the kgdboc post-debug-exception
> handler.  That risks deadlock since schedule_work() is not NMI-safe and,
> even on platforms where the NMI is not directly used for debugging, the
> debug trap can have NMI-like behaviour depending on where breakpoints
> are placed.
> 
> Fix this by using the irq work system, which is NMI-safe, to defer the
> call to schedule_work() to a point when it is safe to call.
> 
> Reported-by: Liuye <liu.yeC@....com>
> Closes: https://lore.kernel.org/all/20240228025602.3087748-1-liu.yeC@h3c.com/
> Cc: stable@...r.kernel.org
> Reviewed-by: Douglas Anderson <dianders@...omium.org>
> Signed-off-by: Daniel Thompson <daniel.thompson@...aro.org>
> ---
> @Greg: I'm assuming this could/should go via your tree but feel free
>        to share an ack if you want me to hoover it up instead.

Hoover away!

Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>