linux-kernel - [PATCH 3/3] drm/vc4: hdmi: Only call into DRM framework if registered

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Date:   Wed,  7 Jul 2021 11:51:12 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     dri-devel@...ts.freedesktop.org,
        Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Maxime Ripard <maxime@...no.tech>
Cc:     Emma Anholt <emma@...olt.net>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org,
        linux-rpi-kernel@...ts.infradead.org,
        bcm-kernel-feedback-list@...adcom.com,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Phil Elwell <phil@...pberrypi.com>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Dom Cobley <dom@...pberrypi.com>,
        Maxime Ripard <mripard@...nel.org>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>
Subject: [PATCH 3/3] drm/vc4: hdmi: Only call into DRM framework if registered

Our hotplug handler will currently call the drm_kms_helper_hotplug_event
every time a hotplug interrupt is called.

However, since the device is registered after all the drivers have
finished their bind callback, we have a window between when we install
our interrupt handler and when drm_dev_register() is eventually called
where our handler can run and call drm_kms_helper_hotplug_event but the
device hasn't been registered yet, causing a null pointer dereference.

Fix this by making sure we only call drm_kms_helper_hotplug_event if our
device has been properly registered.

Fixes: f4790083c7c2 ("drm/vc4: hdmi: Rely on interrupts to handle hotplug")
Signed-off-by: Maxime Ripard <maxime@...no.tech>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 50393a8a42b3..31c28252c5f5 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -1580,7 +1580,7 @@ static irqreturn_t vc4_hdmi_hpd_irq_thread(int irq, void *priv)
 	struct vc4_hdmi *vc4_hdmi = priv;
 	struct drm_device *dev = vc4_hdmi->connector.dev;
 
-	if (dev)
+	if (dev && dev->registered)
 		drm_kms_helper_hotplug_event(dev);
 
 	return IRQ_HANDLED;
-- 
2.31.1