[PATCH v6 02/18] drm/bridge: inno-hdmi: Don't dereference a NULL drm_device on hotplug

[Heiko Stuebner]

Am Freitag, 30. Oktober 2026, 18:43:47 Mitteleuropäische Normalzeit schrieb Heiko Stuebner:
> Am Donnerstag, 29. Oktober 2026, 08:53:36 Mitteleuropäische Normalzeit schrieb Michal Wilczynski:
> > inno_hdmi_irq() passes hdmi->bridge.dev to drm_helper_hpd_irq_event(),
> > which dereferences it in its first statement:
> > 
> > 	if (!dev->mode_config.poll_enabled)
> > 
> > bridge.dev is assigned only by drm_bridge_attach(), but inno_hdmi_bind()
> > unmutes the hotplug interrupt in inno_hdmi_init_hw() and installs the
> > handler well before it attaches the bridge:
> > 
> > 	inno_hdmi_init_hw(hdmi);		/* unmutes hotplug */
> > 	devm_request_threaded_irq(...);		/* handler goes live */
> > 	...
> > 	hdmi->bridge.ddc = inno_hdmi_i2c_adapter(hdmi);
> > 	devm_drm_bridge_add(dev, &hdmi->bridge);
> > 	drm_bridge_attach(...);			/* bridge.dev set here */
> > 
> > The bridge is allocated by devm_drm_bridge_alloc(), which kzalloc()s it,
> > so bridge.dev is NULL for all of that window, and a hotplug event
> > arriving in it enters drm_helper_hpd_irq_event(NULL).
> > 
> > Before the conversion to a bridge the ordering was safe:
> > inno_hdmi_register() called drmm_connector_hdmi_init(), which set
> > connector.dev, before the interrupt was requested.
> > 
> > Drop hotplug events that arrive before the bridge is attached.
> > 
> > Fixes: 969325a2597e ("drm/rockchip: inno-hdmi: Convert to drm bridge")
> > Signed-off-by: Michal Wilczynski <m.wilczynski at samsung.com>
> > ---
> >  drivers/gpu/drm/bridge/inno-hdmi.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/bridge/inno-hdmi.c b/drivers/gpu/drm/bridge/inno-hdmi.c
> > index d7c33b92e2ddf4ced84d17304463f44be52270b8..d29832249b942dec84fb9d07a0b21ee751fc0486 100644
> > --- a/drivers/gpu/drm/bridge/inno-hdmi.c
> > +++ b/drivers/gpu/drm/bridge/inno-hdmi.c
> > @@ -929,7 +929,13 @@ static irqreturn_t inno_hdmi_irq(int irq, void *dev_id)
> >  {
> >  	struct inno_hdmi *hdmi = dev_id;
> >  
> > -	drm_helper_hpd_irq_event(hdmi->bridge.dev);
> > +	/*
> > +	 * The interrupt is requested before the bridge is attached, and
> > +	 * bridge.dev is only set by drm_bridge_attach(). Drop hotplug events
> > +	 * that arrive before then rather than dereference a NULL drm_device.
> > +	 */

nit: I don't think that huge comment is necessary for that


> > +	if (hdmi->bridge.dev)
> > +		drm_helper_hpd_irq_event(hdmi->bridge.dev);
> 
> Reviewed-by: Heiko Stuebner <heiko at sntech.de>
> 
> Most other callers of drm_helper_hpd_irq_event() also do exactly this.
> 
> 
> Heiko
>