ACPI: sysfs: validate return type of _STR method

Only buffer objects are valid return values of _STR.

If something else is returned description_show() will access invalid
memory.

Fixes: d1efe3c ("ACPI: Add new sysfs interface to export device description")
Cc: All applicable <[email protected]>
Signed-off-by: Thomas Weißschuh <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Rafael J. Wysocki <[email protected]>

Author: t-8ch

drivers/acpi/device_sysfs.c

@@ -540,8 +540,9 @@ int acpi_device_setup_files(struct acpi_device *dev)
 	 * If device has _STR, 'description' file is created
 	 */
 	if (acpi_has_method(dev->handle, "_STR")) {
-		status = acpi_evaluate_object(dev->handle, "_STR",
-					NULL, &buffer);
+		status = acpi_evaluate_object_typed(dev->handle, "_STR",
+						    NULL, &buffer,
+						    ACPI_TYPE_BUFFER);
 		if (ACPI_FAILURE(status))
 			buffer.pointer = NULL;
 		dev->pnp.str_obj = buffer.pointer;