From: Harry Wentland Date: Thu, 7 May 2026 19:38:37 +0000 (-0400) Subject: drm/amd/display: Clamp HDMI HDCP2 rx_id_list read to buffer size X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=f0f3981c43b32cadfe373d636d9e9ca522bb3702;p=thirdparty%2Fkernel%2Flinux.git drm/amd/display: Clamp HDMI HDCP2 rx_id_list read to buffer size [Why & How] During HDCP 2.x repeater authentication over HDMI, the driver reads the sink's RxStatus register and extracts a 10-bit message size field (max value 1023). This value is used as the read length for the ReceiverID list without being clamped to the size of the destination buffer rx_id_list[177]. A malicious HDMI repeater could advertise a message size larger than the buffer, causing an out-of-bounds write during the I2C read. Clamp the read length in mod_hdcp_read_rx_id_list() to the size of the rx_id_list buffer, matching the approach already used in the DP branch. Fixes: eff682f83c9c ("drm/amd/display: Add DDC handles for HDCP2.2") Assisted-by: Copilot:claude-opus-4.6 Reviewed-by: Alex Hung Signed-off-by: Harry Wentland Signed-off-by: Ray Wu Tested-by: Daniel Wheeler Signed-off-by: Alex Deucher (cherry picked from commit 229212219e4247d9486f8ba41ef087358490be09) Cc: stable@vger.kernel.org --- diff --git a/drivers/gpu/drm/amd/display/modules/hdcp/hdcp_ddc.c b/drivers/gpu/drm/amd/display/modules/hdcp/hdcp_ddc.c index 0ca39873f807..324413a090bf 100644 --- a/drivers/gpu/drm/amd/display/modules/hdcp/hdcp_ddc.c +++ b/drivers/gpu/drm/amd/display/modules/hdcp/hdcp_ddc.c @@ -529,7 +529,8 @@ enum mod_hdcp_status mod_hdcp_read_rx_id_list(struct mod_hdcp *hdcp) } else { status = read(hdcp, MOD_HDCP_MESSAGE_ID_READ_REPEATER_AUTH_SEND_RECEIVERID_LIST, hdcp->auth.msg.hdcp2.rx_id_list, - hdcp->auth.msg.hdcp2.rx_id_list_size); + MIN(hdcp->auth.msg.hdcp2.rx_id_list_size, + sizeof(hdcp->auth.msg.hdcp2.rx_id_list))); } return status; }