linux-kernel - Re: [PATCH v3] drm/panthor: Fix UAF race between device unplug and FW event processing

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Message-ID: <aQi-agymuWjgJA3h@e110455-lin.cambridge.arm.com>
Date: Mon, 3 Nov 2025 14:38:34 +0000
From: Liviu Dudau <liviu.dudau@....com>
To: Ketil Johnsen <ketil.johnsen@....com>
Cc: Boris Brezillon <boris.brezillon@...labora.com>,
	Steven Price <steven.price@....com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Heiko Stuebner <heiko@...ech.de>, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] drm/panthor: Fix UAF race between device unplug and
 FW event processing

On Mon, Oct 27, 2025 at 03:02:15PM +0100, Ketil Johnsen wrote:
> The function panthor_fw_unplug() will free the FW memory sections.
> The problem is that there could still be pending FW events which are yet
> not handled at this point. process_fw_events_work() can in this case try
> to access said freed memory.
> 
> Simply call disable_work_sync() to both drain and prevent future
> invocation of process_fw_events_work().
> 
> Signed-off-by: Ketil Johnsen <ketil.johnsen@....com>
> Fixes: de85488138247 ("drm/panthor: Add the scheduler logical block")

Pushed to drm-misc-next.

Best regards,
Liviu

> ---
> v2:
> - Followed Boris's advice and handle the race purely within the
>   scheduler block (by adding a destroyed state)
> 
> v3:
> - New approach, one single call to disable_work_sync()
> ---
>  drivers/gpu/drm/panthor/panthor_sched.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
> index 0cc9055f4ee52..b7595beaa0205 100644
> --- a/drivers/gpu/drm/panthor/panthor_sched.c
> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> @@ -3880,6 +3880,7 @@ void panthor_sched_unplug(struct panthor_device *ptdev)
>  	struct panthor_scheduler *sched = ptdev->scheduler;
>  
>  	cancel_delayed_work_sync(&sched->tick_work);
> +	disable_work_sync(&sched->fw_events_work);
>  
>  	mutex_lock(&sched->lock);
>  	if (sched->pm.has_ref) {
> -- 
> 2.47.2
> 

-- 
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