[PATCH] drm/amd/display: dcn314: clamp NumDfPstatesEnabled to table size

[Kery Qi <qikeyu2017@gmail.com>]

NumDfPstatesEnabled from SMU/PMFW is used to iterate over DfPstateTable[]
in dcn314_clk_mgr_helper_populate_bw_params(). The value is not validated
against the maximum number of DF P-states supported.

Although we have not observed any firmware returning an invalid value,
an oversized NumDfPstatesEnabled could cause an out-of-bounds read.

A similar bounds issue in dcn35_clkmgr was previously fixed and assigned
CVE-2024-26699. This patch applies the same defensive check to dcn314.

Clamp NumDfPstatesEnabled to NUM_DF_PSTATE_LEVELS before using it.

Fixes: 19f7b8334484 ("drm/amd/display: Update clock table policy for DCN314")
Signed-off-by: Kery Qi <qikeyu2017@gmail.com>
---
 .../drm/amd/display/dc/clk_mgr/dcn314/dcn314_clk_mgr.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn314/dcn314_clk_mgr.c b/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn314/dcn314_clk_mgr.c
index db687a13174d..50ea75d974fd 100644
--- a/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn314/dcn314_clk_mgr.c
+++ b/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn314/dcn314_clk_mgr.c
@@ -754,9 +754,15 @@ static void dcn314_clk_mgr_helper_populate_bw_params(struct clk_mgr_internal *cl
 	struct clk_limit_table_entry def_max = bw_params->clk_table.entries[bw_params->clk_table.num_entries - 1];
 	uint32_t max_pstate = 0,  max_fclk = 0,  min_pstate = 0, max_dispclk = 0, max_dppclk = 0;
 	int i;
+	/* Clamp NumDfPstatesEnabled to avoid out-of-bounds access */
+	uint8_t num_memps = clock_table->NumDfPstatesEnabled;
+
+	if (num_memps > NUM_DF_PSTATE_LEVELS) {
+		num_memps = NUM_DF_PSTATE_LEVELS;
+	}
 
 	/* Find highest valid fclk pstate */
-	for (i = 0; i < clock_table->NumDfPstatesEnabled; i++) {
+	for (i = 0; i < num_memps; i++) {
 		if (is_valid_clock_value(clock_table->DfPstateTable[i].FClk) &&
 		    clock_table->DfPstateTable[i].FClk > max_fclk) {
 			max_fclk = clock_table->DfPstateTable[i].FClk;
@@ -782,7 +788,7 @@ static void dcn314_clk_mgr_helper_populate_bw_params(struct clk_mgr_internal *cl
 		uint32_t min_fclk = clock_table->DfPstateTable[0].FClk;
 		int j;
 
-		for (j = 1; j < clock_table->NumDfPstatesEnabled; j++) {
+		for (j = 1; j < num_memps; j++) {
 			if (is_valid_clock_value(clock_table->DfPstateTable[j].FClk) &&
 			    clock_table->DfPstateTable[j].FClk < min_fclk &&
 			    clock_table->DfPstateTable[j].Voltage <= clock_table->SocVoltage[i]) {
-- 
2.34.1