drm/amd/display: Fix array-index-out-of-bounds in dcn35_clkmgr

[Why]
There is a potential memory access violation while
iterating through array of dcn35 clks.

[How]
Limit iteration per array size.

Cc: Mario Limonciello <[email protected]>
Cc: Alex Deucher <[email protected]>
Cc: [email protected]
Reviewed-by: Nicholas Kazlauskas <[email protected]>
Acked-by: Aurabindo Pillai <[email protected]>
Signed-off-by: Roman Li <[email protected]>
Tested-by: Daniel Wheeler <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>

Author: Roman Li

drivers/gpu/drm/amd/display/dc/clk_mgr/dcn35/dcn35_clk_mgr.c

@@ -655,10 +655,13 @@ static void dcn35_clk_mgr_helper_populate_bw_params(struct clk_mgr_internal *clk
 	struct clk_limit_table_entry def_max = bw_params->clk_table.entries[bw_params->clk_table.num_entries - 1];
 	uint32_t max_fclk = 0, min_pstate = 0, max_dispclk = 0, max_dppclk = 0;
 	uint32_t max_pstate = 0, max_dram_speed_mts = 0, min_dram_speed_mts = 0;
+	uint32_t num_memps, num_fclk, num_dcfclk;
 	int i;
 
 	/* Determine min/max p-state values. */
-	for (i = 0; i < clock_table->NumMemPstatesEnabled; i++) {
+	num_memps = (clock_table->NumMemPstatesEnabled > NUM_MEM_PSTATE_LEVELS) ? NUM_MEM_PSTATE_LEVELS :
+		clock_table->NumMemPstatesEnabled;
+	for (i = 0; i < num_memps; i++) {
 		uint32_t dram_speed_mts = calc_dram_speed_mts(&clock_table->MemPstateTable[i]);
 
 		if (is_valid_clock_value(dram_speed_mts) && dram_speed_mts > max_dram_speed_mts) {
@@ -670,7 +673,7 @@ static void dcn35_clk_mgr_helper_populate_bw_params(struct clk_mgr_internal *clk
 	min_dram_speed_mts = max_dram_speed_mts;
 	min_pstate = max_pstate;
 
-	for (i = 0; i < clock_table->NumMemPstatesEnabled; i++) {
+	for (i = 0; i < num_memps; i++) {
 		uint32_t dram_speed_mts = calc_dram_speed_mts(&clock_table->MemPstateTable[i]);
 
 		if (is_valid_clock_value(dram_speed_mts) && dram_speed_mts < min_dram_speed_mts) {
@@ -699,9 +702,13 @@ static void dcn35_clk_mgr_helper_populate_bw_params(struct clk_mgr_internal *clk
 	/* Base the clock table on dcfclk, need at least one entry regardless of pmfw table */
 	ASSERT(clock_table->NumDcfClkLevelsEnabled > 0);
 
-	max_fclk = find_max_clk_value(clock_table->FclkClocks_Freq, clock_table->NumFclkLevelsEnabled);
+	num_fclk = (clock_table->NumFclkLevelsEnabled > NUM_FCLK_DPM_LEVELS) ? NUM_FCLK_DPM_LEVELS :
+		clock_table->NumFclkLevelsEnabled;
+	max_fclk = find_max_clk_value(clock_table->FclkClocks_Freq, num_fclk);
 
-	for (i = 0; i < clock_table->NumDcfClkLevelsEnabled; i++) {
+	num_dcfclk = (clock_table->NumFclkLevelsEnabled > NUM_DCFCLK_DPM_LEVELS) ? NUM_DCFCLK_DPM_LEVELS :
+		clock_table->NumDcfClkLevelsEnabled;
+	for (i = 0; i < num_dcfclk; i++) {
 		int j;
 
 		/* First search defaults for the clocks we don't read using closest lower or equal default dcfclk */