[PATCH] drm: mxsfb: Fix NULL pointer dereference crash on unload

[Marek Vasut]

On 10/17/21 7:52 PM, Sam Ravnborg wrote:
> Hi Marek,
> 
> On Wed, Sep 08, 2021 at 08:24:20PM +0200, Daniel Vetter wrote:
>> On Tue, Sep 07, 2021 at 04:49:00AM +0200, Marek Vasut wrote:
>>> The mxsfb->crtc.funcs may already be NULL when unloading the driver,
>>> in which case calling mxsfb_irq_disable() via drm_irq_uninstall() from
>>> mxsfb_unload() leads to NULL pointer dereference.
>>>
>>> Since all we care about is masking the IRQ and mxsfb->base is still
>>> valid, just use that to clear and mask the IRQ.
>>>
>>> Fixes: ae1ed00932819 ("drm: mxsfb: Stop using DRM simple display pipeline helper")
>>> Signed-off-by: Marek Vasut <marex at denx.de>
>>> Cc: Daniel Abrecht <public at danielabrecht.ch>
>>> Cc: Emil Velikov <emil.l.velikov at gmail.com>
>>> Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
>>> Cc: Sam Ravnborg <sam at ravnborg.org>
>>> Cc: Stefan Agner <stefan at agner.ch>
>>
>> You probably want a drm_atomic_helper_shutdown instead of trying to do all
>> that manually. We've also added a bunch more devm and drmm_ functions to
>> automate the cleanup a lot more here, e.g. your drm_mode_config_cleanup is
>> in the wrong place.
> 
> I have applied v2 of this patch today - but failed to see any response
> in v2 to this comment from Daniel. Was it lost somehow?

Hmmm, I'll investigate that ^ in the next round of mxsfb clean ups.