linux-kernel - Re: [PATCH] drm/panthor: Fix NULL pointer dereference on panthor_fw

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Message-ID: <aUFV6chRKx7aoQ5z@e142607>
Date: Tue, 16 Dec 2025 12:51:53 +0000
From: Liviu Dudau <liviu.dudau@....com>
To: Karunika Choo <karunika.choo@....com>
Cc: dri-devel@...ts.freedesktop.org, nd@....com,
	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>,
	linux-kernel@...r.kernel.org, aishwarya.tcv@....com
Subject: Re: [PATCH] drm/panthor: Fix NULL pointer dereference on
 panthor_fw_unplug

On Mon, Dec 15, 2025 at 08:33:12PM +0000, Karunika Choo wrote:
> This patch removes the MCU halt and wait for halt procedures during
> panthor_fw_unplug() as the MCU can be in a variety of states or the FW
> may not even be loaded/initialized at all, the latter of which can lead
> to a NULL pointer dereference.
> 
> It should be safe on unplug to just disable the MCU without waiting for
> it to halt as it may not be able to.
> 
> Fixes: 514072549865 ("drm/panthor: Support GLB_REQ.STATE field for Mali-G1 GPUs")
> Suggested-by: Boris Brezillon <boris.brezillon@...labora.com>
> Signed-off-by: Karunika Choo <karunika.choo@....com>

Reviewed-by: Liviu Dudau <liviu@...au.co.uk>

Best regards,
Liviu

> ---
>  drivers/gpu/drm/panthor/panthor_fw.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_fw.c b/drivers/gpu/drm/panthor/panthor_fw.c
> index 4beaa589ba66..a64ec8756bed 100644
> --- a/drivers/gpu/drm/panthor/panthor_fw.c
> +++ b/drivers/gpu/drm/panthor/panthor_fw.c
> @@ -1261,10 +1261,6 @@ void panthor_fw_unplug(struct panthor_device *ptdev)
>  		if (ptdev->fw->irq.irq)
>  			panthor_job_irq_suspend(&ptdev->fw->irq);
>  
> -		panthor_fw_halt_mcu(ptdev);
> -		if (!panthor_fw_wait_mcu_halted(ptdev))
> -			drm_warn(&ptdev->base, "Failed to halt MCU on unplug");
> -
>  		panthor_fw_stop(ptdev);
>  	}
>  
> -- 
> 2.49.0
>