Messages in this thread |  | | Date | Tue, 5 May 2026 11:34:36 +0200 | | From | Thorsten Blum <> | | Subject | Re: [PATCH] drm/vc4: fix NULL dereference in vc4_hvs_unbind |
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Hi Dave,
On Tue, May 05, 2026 at 09:54:53AM +0100, Dave Stevenson wrote: > Hi Thorsten > > On Sat, 2 May 2026 at 13:13, Thorsten Blum <thorsten.blum@linux.dev> wrote: > > > > With 'dtoverlay=vc4-kms-v3d,noaudio' and 'hdmi=off' on Raspberry Pi, > > Mainline doesn't use overlays, so this description isn't valid. > > Which generation of Pi are you using? Whilst they all share the vc4 > driver, the functionality associated differs. If you're disabling HDMI > (and HDMI audio), which display outputs are you using?
It's a Pi 500 currently running headless, which is why I turned audio and HDMI off. I ended up using:
dtparam=audio=off #dtoverlay=vc4-kms-v3d hdmi=off
This prevents the vc4 and snd modules from loading and works for me.
> > unloading the vc4 module calls vc4_hvs_unbind() with > > dev_get_drvdata(master) returning NULL. > > > > Return early when 'drm' is NULL before converting it to 'vc4' and before > > dereferencing 'vc4->hvs', preventing a kernel oops. > > That leaves things allocated and clocks running, so bailing out isn't a fix. > I'll have a look to see why dev_get_drvdata is returning NULL.
Yes, I realized there are probably other things that need to be fixed. However, the defensive NULL check avoided the kernel oops for me.
Thanks, Thorsten
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