[PATCH 5.15.y] drm/i915/hdcp: check streams[] bounds before overflow

From: Jani Nikula <[email protected]>

[ Upstream commit bbb15a6b042d02e5508a02b4847e02d2579ee7bc ]

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 <[email protected]>
Fixes: e03187e12cae ("drm/i915/hdcp: MST streams support in hdcp port_data")
Cc: [email protected] # v5.12+
Cc: Anshuman Gupta <[email protected]>
Cc: Suraj Kandpal <[email protected]>
Reviewed-by: Suraj Kandpal <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jani Nikula <[email protected]>
(cherry picked from commit 9284ab3b6e776c315883ac2611283d263c9460fd)
Signed-off-by: Joonas Lahtinen <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
---
 drivers/gpu/drm/i915/display/intel_hdcp.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c b/drivers/gpu/drm/i915/display/intel_hdcp.c
index ebc2e32aec0bc..cc159d9261456 100644
--- a/drivers/gpu/drm/i915/display/intel_hdcp.c
+++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
@@ -89,6 +89,9 @@ intel_hdcp_required_content_stream(struct intel_digital_port *dig_port)
 		if (!enforce_type0 && !intel_streams_type1_capable(connector))
 			enforce_type0 = true;
 
+		if (drm_WARN_ON(&i915->drm, data->k >= INTEL_NUM_PIPES(i915)))
+			return -EINVAL;
+
 		data->streams[data->k].stream_id = intel_conn_to_vcpi(connector);
 		data->k++;
 
@@ -98,7 +101,7 @@ intel_hdcp_required_content_stream(struct intel_digital_port *dig_port)
 	}
 	drm_connector_list_iter_end(&conn_iter);
 
-	if (drm_WARN_ON(&i915->drm, data->k > INTEL_NUM_PIPES(i915) || data->k == 0))
+	if (drm_WARN_ON(&i915->drm, !data->k))
 		return -EINVAL;
 
 	/*
-- 
2.53.0