[PATCH] drm/display: hdmi: Prevent NULL pointer dereference in sync_scdc()

[PATCH] drm/display: hdmi: Prevent NULL pointer dereference in sync_scdc()

[Cristian Ciocaltea]

The connector pointer is used to initialize the local variables hdmi and
dev before the NULL check takes place, leading to the following Smatch
complaint:

  drivers/gpu/drm/display/drm_hdmi_helper.c:663 drm_connector_hdmi_sync_scdc()
  warn: variable dereferenced before check 'connector' (see line 657)

Move those initializations after the sanity check to avoid a potential
NULL pointer dereference.

Fixes: d653818324ed ("drm/display: hdmi: Add HDMI 2.0 scrambling management helpers")
Reported-by: Dan Carpenter <error27@gmail.com>
Closes: https://lore.kernel.org/all/arJo7A7L5hud3tyc@stanley.mountain/
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
---
 drivers/gpu/drm/display/drm_hdmi_helper.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_hdmi_helper.c b/drivers/gpu/drm/display/drm_hdmi_helper.c
index f85cce3d6254..872f7e32e8d2 100644
--- a/drivers/gpu/drm/display/drm_hdmi_helper.c
+++ b/drivers/gpu/drm/display/drm_hdmi_helper.c
@@ -653,9 +653,9 @@ EXPORT_SYMBOL(drm_connector_hdmi_disable_scrambling);
 int drm_connector_hdmi_sync_scdc(struct drm_connector *connector, bool plugged,
 				 struct drm_modeset_acquire_ctx *ctx)
 {
-	struct drm_connector_hdmi *hdmi = &connector->hdmi;
-	struct drm_device *dev = connector->dev;
+	struct drm_connector_hdmi *hdmi;
 	struct drm_connector_state *conn_state;
+	struct drm_device *dev;
 	struct drm_crtc *crtc;
 	u8 config;
 	int ret;
@@ -663,6 +663,9 @@ int drm_connector_hdmi_sync_scdc(struct drm_connector *connector, bool plugged,
 	if (!connector || !plugged || !ctx)
 		return 0;
 
+	hdmi = &connector->hdmi;
+	dev = connector->dev;
+
 	/*
 	 * This is normally part of .detect_ctx() call path, which already holds
 	 * connection_mutex through @ctx.  However, re-acquiring it with the

---
base-commit: 37b346eab23aead52d17a8fa687056bfc651a416
change-id: 20261002-hdmi-sync-scdc-fix-deref-1813077dd48a

Re: [PATCH] drm/display: hdmi: Prevent NULL pointer dereference in sync_scdc()

[Cristian Ciocaltea]

Hi,

On 10/2/26 1:26 AM, Cristian Ciocaltea wrote:
> The connector pointer is used to initialize the local variables hdmi and
> dev before the NULL check takes place, leading to the following Smatch
> complaint:
> 
>   drivers/gpu/drm/display/drm_hdmi_helper.c:663 drm_connector_hdmi_sync_scdc()
>   warn: variable dereferenced before check 'connector' (see line 657)
> 
> Move those initializations after the sanity check to avoid a potential
> NULL pointer dereference.
> 
> Fixes: d653818324ed ("drm/display: hdmi: Add HDMI 2.0 scrambling management helpers")

There are a couple of additional fixes on top of this one, which is why I've
sent them together as part of a new series:

https://lore.kernel.org/all/20261104-hdmi-scdc-scramb-fixes-v1-0-16a9bb3d64a6@collabora.com/

Thanks,
Cristian