drm/radeon: fix handling of v6 power tables

The code was mis-handling variable sized arrays.
Reported-by: Sylvain BERTRAND <sylware@legeek.net>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/radeon/radeon_atombios.c

@@ -2518,6 +2518,7 @@ static int radeon_atombios_parse_power_table_6(struct radeon_device *rdev)
 	int index = GetIndexIntoMasterTable(DATA, PowerPlayInfo);
         u16 data_offset;
 	u8 frev, crev;
+	u8 *power_state_offset;
 
 	if (!atom_parse_data_header(mode_info->atom_context, index, NULL,
 				   &frev, &crev, &data_offset))
@@ -2540,11 +2541,11 @@ static int radeon_atombios_parse_power_table_6(struct radeon_device *rdev)
 				       state_array->ucNumEntries, GFP_KERNEL);
 	if (!rdev->pm.power_state)
 		return state_index;
+	power_state_offset = (u8 *)state_array->states;
 	for (i = 0; i < state_array->ucNumEntries; i++) {
 		mode_index = 0;
-		power_state = (union pplib_power_state *)&state_array->states[i];
-		/* XXX this might be an inagua bug... */
-		non_clock_array_index = i; /* power_state->v2.nonClockInfoIndex */
+		power_state = (union pplib_power_state *)power_state_offset;
+		non_clock_array_index = power_state->v2.nonClockInfoIndex;
 		non_clock_info = (struct _ATOM_PPLIB_NONCLOCK_INFO *)
 			&non_clock_info_array->nonClockInfo[non_clock_array_index];
 		rdev->pm.power_state[i].clock_info = kzalloc(sizeof(struct radeon_pm_clock_info) *
@@ -2556,9 +2557,6 @@ static int radeon_atombios_parse_power_table_6(struct radeon_device *rdev)
 		if (power_state->v2.ucNumDPMLevels) {
 			for (j = 0; j < power_state->v2.ucNumDPMLevels; j++) {
 				clock_array_index = power_state->v2.clockInfoIndex[j];
-				/* XXX this might be an inagua bug... */
-				if (clock_array_index >= clock_info_array->ucNumEntries)
-					continue;
 				clock_info = (union pplib_clock_info *)
 					&clock_info_array->clockInfo[clock_array_index * clock_info_array->ucEntrySize];
 				valid = radeon_atombios_parse_pplib_clock_info(rdev,
@@ -2580,6 +2578,7 @@ static int radeon_atombios_parse_power_table_6(struct radeon_device *rdev)
 								   non_clock_info);
 			state_index++;
 		}
+		power_state_offset += 2 + power_state->v2.ucNumDPMLevels;
 	}
 	/* if multiple clock modes, mark the lowest as no display */
 	for (i = 0; i < state_index; i++) {