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From:   Colin King <colin.king@canonical.com>
To:     Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Ramalingam C <ramalingam.c@intel.com>,
        Anshuman Gupta <anshuman.gupta@intel.com>,
        intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org
Cc:     kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH][next] drm/i915/hdcp: Fix null pointer dereference of connector->encoder
Date:   Tue, 23 Feb 2021 19:19:09 +0000
Message-Id: <20210223191909.16682-1-colin.king@canonical.com>
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From: Colin Ian King <colin.king@canonical.com>

The recent commit 6c63e6e14da7 ("drm/i915/hdcp: No HDCP when encoder
is't initialized") added a null pointer check on connector->encoder
hence implying that it could potentially be null.  This means that
the initialization of dig_port via the call intel_attached_dig_port
may cause a null pointer dereference on connector->encoder. Fix
this by only assigning dig_port after a null check has been performed
on connector->encoder.

Addresses-Coverity: ("Dereference before null check")
Fixes: 36e5e7042b20 ("drm/i915: Don't fully disable HDCP on a port if multiple pipes are using it")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/gpu/drm/i915/display/intel_hdcp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c b/drivers/gpu/drm/i915/display/intel_hdcp.c
index ae1371c36a32..7525ea31766c 100644
--- a/drivers/gpu/drm/i915/display/intel_hdcp.c
+++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
@@ -2260,7 +2260,7 @@ int intel_hdcp_enable(struct intel_connector *connector,
 		      const struct intel_crtc_state *pipe_config, u8 content_type)
 {
 	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
-	struct intel_digital_port *dig_port = intel_attached_dig_port(connector);
+	struct intel_digital_port *dig_port;
 	struct intel_hdcp *hdcp = &connector->hdcp;
 	unsigned long check_link_interval = DRM_HDCP_CHECK_PERIOD_MS;
 	int ret = -EINVAL;
@@ -2274,6 +2274,7 @@ int intel_hdcp_enable(struct intel_connector *connector,
 		return -ENODEV;
 	}
 
+	dig_port = intel_attached_dig_port(connector);
 	mutex_lock(&hdcp->mutex);
 	mutex_lock(&dig_port->hdcp_mutex);
 	drm_WARN_ON(&dev_priv->drm,
-- 
2.30.0