drm/amd/display: Clamp VBIOS HDMI retimer register count to array size

[Why & How]
The VBIOS integrated info tables (v1_11 and v2_1) contain HdmiRegNum and
Hdmi6GRegNum fields that are used as loop bounds when copying retimer I2C
register settings into fixed-size arrays (dp*_ext_hdmi_reg_settings[9]
and dp*_ext_hdmi_6g_reg_settings[3]). These u8 fields are not validated
before use, so a malformed VBIOS can specify values up to 255, causing an
out-of-bounds heap write during driver probe.

Clamp each register count to the destination array size using min_t()
before the copy loops, in both get_integrated_info_v11() and
get_integrated_info_v2_1().

Assisted-by: GitHub 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 5a7f0ef90195940c54b0f5bb85b87da55f038c69)
Cc: stable@vger.kernel.org

1 files changed, 32 insertions, 16 deletions

diff --git a/drivers/gpu/drm/amd/display/dc/bios/bios_parser2.c b/drivers/gpu/drm/amd/display/dc/bios/bios_parser2.c
index c51c4b2c6fae..e8d8947c552e 100644
--- a/drivers/gpu/drm/amd/display/dc/bios/bios_parser2.c
+++ b/drivers/gpu/drm/amd/display/dc/bios/bios_parser2.c
@@ -2600,14 +2600,16 @@ static enum bp_result get_integrated_info_v11(
 	info_v11->extdispconninfo.checksum;
 
 	info->dp0_ext_hdmi_slv_addr = info_v11->dp0_retimer_set.HdmiSlvAddr;
-	info->dp0_ext_hdmi_reg_num = info_v11->dp0_retimer_set.HdmiRegNum;
+	info->dp0_ext_hdmi_reg_num = min_t(u8, info_v11->dp0_retimer_set.HdmiRegNum,
+					    ARRAY_SIZE(info->dp0_ext_hdmi_reg_settings));
 	for (i = 0; i < info->dp0_ext_hdmi_reg_num; i++) {
 		info->dp0_ext_hdmi_reg_settings[i].i2c_reg_index =
 				info_v11->dp0_retimer_set.HdmiRegSetting[i].ucI2cRegIndex;
 		info->dp0_ext_hdmi_reg_settings[i].i2c_reg_val =
 				info_v11->dp0_retimer_set.HdmiRegSetting[i].ucI2cRegVal;
 	}
-	info->dp0_ext_hdmi_6g_reg_num = info_v11->dp0_retimer_set.Hdmi6GRegNum;
+	info->dp0_ext_hdmi_6g_reg_num = min_t(u8, info_v11->dp0_retimer_set.Hdmi6GRegNum,
+					       ARRAY_SIZE(info->dp0_ext_hdmi_6g_reg_settings));
 	for (i = 0; i < info->dp0_ext_hdmi_6g_reg_num; i++) {
 		info->dp0_ext_hdmi_6g_reg_settings[i].i2c_reg_index =
 				info_v11->dp0_retimer_set.Hdmi6GhzRegSetting[i].ucI2cRegIndex;
@@ -2616,14 +2618,16 @@ static enum bp_result get_integrated_info_v11(
 	}
 
 	info->dp1_ext_hdmi_slv_addr = info_v11->dp1_retimer_set.HdmiSlvAddr;
-	info->dp1_ext_hdmi_reg_num = info_v11->dp1_retimer_set.HdmiRegNum;
+	info->dp1_ext_hdmi_reg_num = min_t(u8, info_v11->dp1_retimer_set.HdmiRegNum,
+					    ARRAY_SIZE(info->dp1_ext_hdmi_reg_settings));
 	for (i = 0; i < info->dp1_ext_hdmi_reg_num; i++) {
 		info->dp1_ext_hdmi_reg_settings[i].i2c_reg_index =
 				info_v11->dp1_retimer_set.HdmiRegSetting[i].ucI2cRegIndex;
 		info->dp1_ext_hdmi_reg_settings[i].i2c_reg_val =
 				info_v11->dp1_retimer_set.HdmiRegSetting[i].ucI2cRegVal;
 	}
-	info->dp1_ext_hdmi_6g_reg_num = info_v11->dp1_retimer_set.Hdmi6GRegNum;
+	info->dp1_ext_hdmi_6g_reg_num = min_t(u8, info_v11->dp1_retimer_set.Hdmi6GRegNum,
+					       ARRAY_SIZE(info->dp1_ext_hdmi_6g_reg_settings));
 	for (i = 0; i < info->dp1_ext_hdmi_6g_reg_num; i++) {
 		info->dp1_ext_hdmi_6g_reg_settings[i].i2c_reg_index =
 				info_v11->dp1_retimer_set.Hdmi6GhzRegSetting[i].ucI2cRegIndex;
@@ -2632,14 +2636,16 @@ static enum bp_result get_integrated_info_v11(
 	}
 
 	info->dp2_ext_hdmi_slv_addr = info_v11->dp2_retimer_set.HdmiSlvAddr;
-	info->dp2_ext_hdmi_reg_num = info_v11->dp2_retimer_set.HdmiRegNum;
+	info->dp2_ext_hdmi_reg_num = min_t(u8, info_v11->dp2_retimer_set.HdmiRegNum,
+					    ARRAY_SIZE(info->dp2_ext_hdmi_reg_settings));
 	for (i = 0; i < info->dp2_ext_hdmi_reg_num; i++) {
 		info->dp2_ext_hdmi_reg_settings[i].i2c_reg_index =
 				info_v11->dp2_retimer_set.HdmiRegSetting[i].ucI2cRegIndex;
 		info->dp2_ext_hdmi_reg_settings[i].i2c_reg_val =
 				info_v11->dp2_retimer_set.HdmiRegSetting[i].ucI2cRegVal;
 	}
-	info->dp2_ext_hdmi_6g_reg_num = info_v11->dp2_retimer_set.Hdmi6GRegNum;
+	info->dp2_ext_hdmi_6g_reg_num = min_t(u8, info_v11->dp2_retimer_set.Hdmi6GRegNum,
+					       ARRAY_SIZE(info->dp2_ext_hdmi_6g_reg_settings));
 	for (i = 0; i < info->dp2_ext_hdmi_6g_reg_num; i++) {
 		info->dp2_ext_hdmi_6g_reg_settings[i].i2c_reg_index =
 				info_v11->dp2_retimer_set.Hdmi6GhzRegSetting[i].ucI2cRegIndex;
@@ -2648,14 +2654,16 @@ static enum bp_result get_integrated_info_v11(
 	}
 
 	info->dp3_ext_hdmi_slv_addr = info_v11->dp3_retimer_set.HdmiSlvAddr;
-	info->dp3_ext_hdmi_reg_num = info_v11->dp3_retimer_set.HdmiRegNum;
+	info->dp3_ext_hdmi_reg_num = min_t(u8, info_v11->dp3_retimer_set.HdmiRegNum,
+					    ARRAY_SIZE(info->dp3_ext_hdmi_reg_settings));
 	for (i = 0; i < info->dp3_ext_hdmi_reg_num; i++) {
 		info->dp3_ext_hdmi_reg_settings[i].i2c_reg_index =
 				info_v11->dp3_retimer_set.HdmiRegSetting[i].ucI2cRegIndex;
 		info->dp3_ext_hdmi_reg_settings[i].i2c_reg_val =
 				info_v11->dp3_retimer_set.HdmiRegSetting[i].ucI2cRegVal;
 	}
-	info->dp3_ext_hdmi_6g_reg_num = info_v11->dp3_retimer_set.Hdmi6GRegNum;
+	info->dp3_ext_hdmi_6g_reg_num = min_t(u8, info_v11->dp3_retimer_set.Hdmi6GRegNum,
+					       ARRAY_SIZE(info->dp3_ext_hdmi_6g_reg_settings));
 	for (i = 0; i < info->dp3_ext_hdmi_6g_reg_num; i++) {
 		info->dp3_ext_hdmi_6g_reg_settings[i].i2c_reg_index =
 				info_v11->dp3_retimer_set.Hdmi6GhzRegSetting[i].ucI2cRegIndex;
@@ -2805,14 +2813,16 @@ static enum bp_result get_integrated_info_v2_1(
 	info->ext_disp_conn_info.checksum =
 		info_v2_1->extdispconninfo.checksum;
 	info->dp0_ext_hdmi_slv_addr = info_v2_1->dp0_retimer_set.HdmiSlvAddr;
-	info->dp0_ext_hdmi_reg_num = info_v2_1->dp0_retimer_set.HdmiRegNum;
+	info->dp0_ext_hdmi_reg_num = min_t(u8, info_v2_1->dp0_retimer_set.HdmiRegNum,
+					    ARRAY_SIZE(info->dp0_ext_hdmi_reg_settings));
 	for (i = 0; i < info->dp0_ext_hdmi_reg_num; i++) {
 		info->dp0_ext_hdmi_reg_settings[i].i2c_reg_index =
 				info_v2_1->dp0_retimer_set.HdmiRegSetting[i].ucI2cRegIndex;
 		info->dp0_ext_hdmi_reg_settings[i].i2c_reg_val =
 				info_v2_1->dp0_retimer_set.HdmiRegSetting[i].ucI2cRegVal;
 	}
-	info->dp0_ext_hdmi_6g_reg_num = info_v2_1->dp0_retimer_set.Hdmi6GRegNum;
+	info->dp0_ext_hdmi_6g_reg_num = min_t(u8, info_v2_1->dp0_retimer_set.Hdmi6GRegNum,
+					       ARRAY_SIZE(info->dp0_ext_hdmi_6g_reg_settings));
 	for (i = 0; i < info->dp0_ext_hdmi_6g_reg_num; i++) {
 		info->dp0_ext_hdmi_6g_reg_settings[i].i2c_reg_index =
 				info_v2_1->dp0_retimer_set.Hdmi6GhzRegSetting[i].ucI2cRegIndex;
@@ -2820,14 +2830,16 @@ static enum bp_result get_integrated_info_v2_1(
 				info_v2_1->dp0_retimer_set.Hdmi6GhzRegSetting[i].ucI2cRegVal;
 	}
 	info->dp1_ext_hdmi_slv_addr = info_v2_1->dp1_retimer_set.HdmiSlvAddr;
-	info->dp1_ext_hdmi_reg_num = info_v2_1->dp1_retimer_set.HdmiRegNum;
+	info->dp1_ext_hdmi_reg_num = min_t(u8, info_v2_1->dp1_retimer_set.HdmiRegNum,
+					    ARRAY_SIZE(info->dp1_ext_hdmi_reg_settings));
 	for (i = 0; i < info->dp1_ext_hdmi_reg_num; i++) {
 		info->dp1_ext_hdmi_reg_settings[i].i2c_reg_index =
 				info_v2_1->dp1_retimer_set.HdmiRegSetting[i].ucI2cRegIndex;
 		info->dp1_ext_hdmi_reg_settings[i].i2c_reg_val =
 				info_v2_1->dp1_retimer_set.HdmiRegSetting[i].ucI2cRegVal;
 	}
-	info->dp1_ext_hdmi_6g_reg_num = info_v2_1->dp1_retimer_set.Hdmi6GRegNum;
+	info->dp1_ext_hdmi_6g_reg_num = min_t(u8, info_v2_1->dp1_retimer_set.Hdmi6GRegNum,
+					       ARRAY_SIZE(info->dp1_ext_hdmi_6g_reg_settings));
 	for (i = 0; i < info->dp1_ext_hdmi_6g_reg_num; i++) {
 		info->dp1_ext_hdmi_6g_reg_settings[i].i2c_reg_index =
 				info_v2_1->dp1_retimer_set.Hdmi6GhzRegSetting[i].ucI2cRegIndex;
@@ -2835,14 +2847,16 @@ static enum bp_result get_integrated_info_v2_1(
 				info_v2_1->dp1_retimer_set.Hdmi6GhzRegSetting[i].ucI2cRegVal;
 	}
 	info->dp2_ext_hdmi_slv_addr = info_v2_1->dp2_retimer_set.HdmiSlvAddr;
-	info->dp2_ext_hdmi_reg_num = info_v2_1->dp2_retimer_set.HdmiRegNum;
+	info->dp2_ext_hdmi_reg_num = min_t(u8, info_v2_1->dp2_retimer_set.HdmiRegNum,
+					    ARRAY_SIZE(info->dp2_ext_hdmi_reg_settings));
 	for (i = 0; i < info->dp2_ext_hdmi_reg_num; i++) {
 		info->dp2_ext_hdmi_reg_settings[i].i2c_reg_index =
 				info_v2_1->dp2_retimer_set.HdmiRegSetting[i].ucI2cRegIndex;
 		info->dp2_ext_hdmi_reg_settings[i].i2c_reg_val =
 				info_v2_1->dp2_retimer_set.HdmiRegSetting[i].ucI2cRegVal;
 	}
-	info->dp2_ext_hdmi_6g_reg_num = info_v2_1->dp2_retimer_set.Hdmi6GRegNum;
+	info->dp2_ext_hdmi_6g_reg_num = min_t(u8, info_v2_1->dp2_retimer_set.Hdmi6GRegNum,
+					       ARRAY_SIZE(info->dp2_ext_hdmi_6g_reg_settings));
 	for (i = 0; i < info->dp2_ext_hdmi_6g_reg_num; i++) {
 		info->dp2_ext_hdmi_6g_reg_settings[i].i2c_reg_index =
 				info_v2_1->dp2_retimer_set.Hdmi6GhzRegSetting[i].ucI2cRegIndex;
@@ -2850,14 +2864,16 @@ static enum bp_result get_integrated_info_v2_1(
 				info_v2_1->dp2_retimer_set.Hdmi6GhzRegSetting[i].ucI2cRegVal;
 	}
 	info->dp3_ext_hdmi_slv_addr = info_v2_1->dp3_retimer_set.HdmiSlvAddr;
-	info->dp3_ext_hdmi_reg_num = info_v2_1->dp3_retimer_set.HdmiRegNum;
+	info->dp3_ext_hdmi_reg_num = min_t(u8, info_v2_1->dp3_retimer_set.HdmiRegNum,
+					    ARRAY_SIZE(info->dp3_ext_hdmi_reg_settings));
 	for (i = 0; i < info->dp3_ext_hdmi_reg_num; i++) {
 		info->dp3_ext_hdmi_reg_settings[i].i2c_reg_index =
 				info_v2_1->dp3_retimer_set.HdmiRegSetting[i].ucI2cRegIndex;
 		info->dp3_ext_hdmi_reg_settings[i].i2c_reg_val =
 				info_v2_1->dp3_retimer_set.HdmiRegSetting[i].ucI2cRegVal;
 	}
-	info->dp3_ext_hdmi_6g_reg_num = info_v2_1->dp3_retimer_set.Hdmi6GRegNum;
+	info->dp3_ext_hdmi_6g_reg_num = min_t(u8, info_v2_1->dp3_retimer_set.Hdmi6GRegNum,
+					       ARRAY_SIZE(info->dp3_ext_hdmi_6g_reg_settings));
 	for (i = 0; i < info->dp3_ext_hdmi_6g_reg_num; i++) {
 		info->dp3_ext_hdmi_6g_reg_settings[i].i2c_reg_index =
 				info_v2_1->dp3_retimer_set.Hdmi6GhzRegSetting[i].ucI2cRegIndex;