[PATCH 6.6.y v2 0/2] drm/i915/hdcp: guard both capability checks

[Artem Dinaburg <artem@trailofbits.com>]

Hi Greg, Sasha, and i915 maintainers,

Thanks for catching the second dereference.

The code in patch 1 is unchanged from v1.
As Sasha pointed out, on 6.6.y, however, intel_hdcp_info()
calls intel_hdcp_capable() and then intel_hdcp2_capable(). Guarding only
the first helper therefore moves the debugfs NULL dereference to the next
call.

Patch 2 adapts upstream commit d34f4f058edf ("drm/i915/hdcp: Add encoder
check in hdcp2_get_capability") to the older layout. The 6.6.y tree
predates commit 130849f8ec14 ("drm/i915/hdcp: Use intel_connector as
argument for hdcp_2_2_capable"), so its dereference is still in the common
intel_hdcp2_capable() helper rather than the DP and HDMI shims. The
adaptation puts the encoder guard before that dereference and returns
false through the older bool interface.

The CNA record for CVE-2024-53050 starts its affected range at 6.7, but
that range follows the later shim layout. The same unsafe conversion is
already present in the common helper in 6.6.y.

Together, the two patches make both debugfs capability checks return
false before converting the missing encoder to a digital port. Both fixes
entered mainline before v6.12, so every newer supported stable tree
already contains them. The same common HDCP2 dereference is present in
6.1.y and needs separate handling; this series is only for 6.6.y.

Could you please queue both patches for 6.6.y?

An LLM helped adapt and validate both patches; I reviewed the resulting code
and validation evidence.

Changes in v2:
- add the adapted HDCP2 guard identified during review;
- send the two guards as one series because both are required for the
  debugfs path.

v1: https://lore.kernel.org/r/20260929031728.88004-1-artem@trailofbits.com
Review: https://lore.kernel.org/r/2026-09-29-daily-reply-0012-re-i915-hdcp-encoder-check-v2-6-6@kernel.org

Thanks,
Artem Dinaburg

Suraj Kandpal (2):
  drm/i915/hdcp: Add encoder check in intel_hdcp_get_capability
  drm/i915/hdcp: Add encoder check in hdcp2_get_capability

 drivers/gpu/drm/i915/display/intel_hdcp.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)


base-commit: 79643295eba17affbd16ca97f3ef04c90266b28c
-- 
2.39.5