[PATCH 6.1.y 2/2] drm/i915/hdcp: Add encoder check in hdcp2_get_capability

[Artem Dinaburg <artem@trailofbits.com>]

From: Suraj Kandpal <suraj.kandpal@intel.com>

[ Upstream commit d34f4f058edf1235c103ca9c921dc54820d14d40 ]

Add encoder check in intel_hdcp2_get_capability to avoid
null pointer error.

[ Backport to 6.1.y: upstream adds the check in the DP shim's
  intel_dp_hdcp2_get_capability(), which does not exist here. This tree
  predates the intel_connector conversion of the shims: its
  intel_dp_hdcp2_capable() takes a digital port, and the
  intel_attached_dig_port() lookup is still done in the common
  intel_hdcp2_capable() helper. Put the same encoder guard there, before
  that lookup, and return false through the bool API when no encoder is
  attached. ]

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Dnyaneshwar Bhadane <dnyaneshwar.bhadane@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240722064451.3610512-3-suraj.kandpal@intel.com
Assisted-by: LLM
Signed-off-by: Artem Dinaburg <artem@trailofbits.com>
---
Hi Greg, Sasha, and drm i915 maintainers,

I am working through the small CVE backports still missing from 6.1.y.
This one addresses CVE-2024-53050. It adds the same encoder check to the
HDCP2.2 capability query, which the debugfs path calls right after the
HDCP1.4 one.

The 6.6.y backport went out as the same 2-patch series and has been
picked up for 6.6.y. The fix is already present in 6.12.y, 6.18.y, and
7.2.y, but not in 6.1.y.
The target-specific adjustment is recorded in the bracketed note above.

Could you please queue it for 6.1.y?

CVE: CVE-2024-53050
Upstream: d34f4f058edf1235c103ca9c921dc54820d14d40

AI assistance: An LLM helped identify, adapt, and validate this backport; I
reviewed the resulting code and validation evidence.

Thanks,
Artem Dinaburg

 drivers/gpu/drm/i915/display/intel_hdcp.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c b/drivers/gpu/drm/i915/display/intel_hdcp.c
index 507721c94f2fdd..d31c1f1f0e5074 100644
--- a/drivers/gpu/drm/i915/display/intel_hdcp.c
+++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
@@ -208,11 +208,16 @@ bool intel_hdcp_capable(struct intel_connector *connector)
 /* Is HDCP2.2 capable on Platform and Sink */
 bool intel_hdcp2_capable(struct intel_connector *connector)
 {
-	struct intel_digital_port *dig_port = intel_attached_dig_port(connector);
+	struct intel_digital_port *dig_port;
 	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
 	struct intel_hdcp *hdcp = &connector->hdcp;
 	bool capable = false;
 
+	if (!intel_attached_encoder(connector))
+		return capable;
+
+	dig_port = intel_attached_dig_port(connector);
+
 	/* I915 support for HDCP2.2 */
 	if (!hdcp->hdcp2_supported)
 		return false;
-- 
2.39.5