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drm/amd/display: Clamp HDMI HDCP2 rx_id_list read to buffer size

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[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: eff682f83c ("drm/amd/display: Add DDC handles for HDCP2.2")
Assisted-by: Copilot:claude-opus-4.6
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Ray Wu <ray.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 229212219e)
Cc: stable@vger.kernel.org
This commit is contained in:
Harry Wentland 2026-05-07 15:38:37 -04:00 committed by Alex Deucher
parent 49c3da6596
commit f0f3981c43
1 changed files with 2 additions and 1 deletions
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3
drivers/gpu/drm/amd/display/modules/hdcp/hdcp_ddc.c
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@ -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;
}