drm/radeon: Avoid power table parsing memory leaks

Avoid leaving a hanging pre-allocated clock_info if last mode is
invalid, and avoid heap corruption if no valid modes are found.

Bug: https://bugzilla.kernel.org/show_bug.cgi?id=211537
Fixes: 6991b8f2 ("drm/radeon/kms: fix segfault in pm rework")
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon_atombios.c

@@ -2120,11 +2120,14 @@ static int radeon_atombios_parse_power_table_1_3(struct radeon_device *rdev)
 		return state_index;
 	/* last mode is usually default, array is low to high */
 	for (i = 0; i < num_modes; i++) {
-		rdev->pm.power_state[state_index].clock_info =
-			kcalloc(1, sizeof(struct radeon_pm_clock_info),
-				GFP_KERNEL);
+		/* avoid memory leaks from invalid modes or unknown frev. */
+		if (!rdev->pm.power_state[state_index].clock_info) {
+			rdev->pm.power_state[state_index].clock_info =
+				kzalloc(sizeof(struct radeon_pm_clock_info),
+					GFP_KERNEL);
+		}
 		if (!rdev->pm.power_state[state_index].clock_info)
-			return state_index;
+			goto out;
 		rdev->pm.power_state[state_index].num_clock_modes = 1;
 		rdev->pm.power_state[state_index].clock_info[0].voltage.type = VOLTAGE_NONE;
 		switch (frev) {
@@ -2243,8 +2246,15 @@ static int radeon_atombios_parse_power_table_1_3(struct radeon_device *rdev)
 			break;
 		}
 	}
+out:
+	/* free any unused clock_info allocation. */
+	if (state_index && state_index < num_modes) {
+		kfree(rdev->pm.power_state[state_index].clock_info);
+		rdev->pm.power_state[state_index].clock_info = NULL;
+	}
+
 	/* last mode is usually default */
-	if (rdev->pm.default_power_state_index == -1) {
+	if (state_index && rdev->pm.default_power_state_index == -1) {
 		rdev->pm.power_state[state_index - 1].type =
 			POWER_STATE_TYPE_DEFAULT;
 		rdev->pm.default_power_state_index = state_index - 1;