PCI/ACPI: Validate acpi_pci_set_power_state() parameter

Previously acpi_pci_set_power_state() assumed the requested power state was
valid (PCI_D0 ... PCI_D3cold).  If a caller supplied something else, we
could index outside the state_conv[] array and pass junk to
acpi_device_set_power().

Validate the pci_power_t parameter and return -EINVAL if it's invalid.

Link: https://lore.kernel.org/r/20230621222857.GA122930@bhelgaas
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>

Author: bjorn-helgaas

drivers/pci/pci-acpi.c

@@ -1053,32 +1053,37 @@ int acpi_pci_set_power_state(struct pci_dev *dev, pci_power_t state)
 		[PCI_D3hot] = ACPI_STATE_D3_HOT,
 		[PCI_D3cold] = ACPI_STATE_D3_COLD,
 	};
-	int error = -EINVAL;
+	int error;
 
 	/* If the ACPI device has _EJ0, ignore the device */
 	if (!adev || acpi_has_method(adev->handle, "_EJ0"))
 		return -ENODEV;
 
 	switch (state) {
-	case PCI_D3cold:
-		if (dev_pm_qos_flags(&dev->dev, PM_QOS_FLAG_NO_POWER_OFF) ==
-				PM_QOS_FLAGS_ALL) {
-			error = -EBUSY;
-			break;
-		}
-		fallthrough;
 	case PCI_D0:
 	case PCI_D1:
 	case PCI_D2:
 	case PCI_D3hot:
-		error = acpi_device_set_power(adev, state_conv[state]);
+	case PCI_D3cold:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (state == PCI_D3cold) {
+		if (dev_pm_qos_flags(&dev->dev, PM_QOS_FLAG_NO_POWER_OFF) ==
+				PM_QOS_FLAGS_ALL)
+			return -EBUSY;
 	}
 
-	if (!error)
-		pci_dbg(dev, "power state changed by ACPI to %s\n",
-		        acpi_power_state_string(adev->power.state));
+	error = acpi_device_set_power(adev, state_conv[state]);
+	if (error)
+		return error;
+
+	pci_dbg(dev, "power state changed by ACPI to %s\n",
+	        acpi_power_state_string(adev->power.state));
 
-	return error;
+	return 0;
 }
 
 pci_power_t acpi_pci_get_power_state(struct pci_dev *dev)