drm/i915/hdcp: check streams[] bounds before overflow

The data->streams[] overflow check is done after the buffer overflow has
already happened. Move the overflow check before the write.

Side note, emitting a warning splat with a backtrace might be overkill
here, but prefer not changing the behaviour other than not doing the
overrun.

Discovered using AI-assisted static analysis confirmed by Intel Product
Security.

Reported-by: Martin Hodo <martin.hodo@intel.com>
Fixes: e03187e12cae ("drm/i915/hdcp: MST streams support in hdcp port_data")
Cc: stable@vger.kernel.org # v5.12+
Cc: Anshuman Gupta <anshuman.gupta@intel.com>
Cc: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Link: https://patch.msgid.link/20260625170304.1104723-1-jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
(cherry picked from commit 9284ab3b6e776c315883ac2611283d263c9460fd)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c b/drivers/gpu/drm/i915/display/intel_hdcp.c
index e88fec24af49f00f412c501f02da8988edc71e92..521786a75c42f78ba83cab64b35cd882af2c8c6c 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_hdcp.c
+++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
@@ -145,6 +145,9 @@ intel_hdcp_required_content_stream(struct intel_atomic_state *state,
                if (!new_conn_state || !new_conn_state->crtc)
                        continue;
 
+               if (drm_WARN_ON(display->drm, data->k >= INTEL_NUM_PIPES(display)))
+                       return -EINVAL;
+
                data->streams[data->k].stream_id =
                        intel_conn_to_vcpi(state, connector);
                data->k++;
@@ -155,7 +158,7 @@ intel_hdcp_required_content_stream(struct intel_atomic_state *state,
        }
        drm_connector_list_iter_end(&conn_iter);
 
-       if (drm_WARN_ON(display->drm, data->k > INTEL_NUM_PIPES(display) || data->k == 0))
+       if (drm_WARN_ON(display->drm, !data->k))
                return -EINVAL;
 
        /*