HID: hiddev: validate num_values for HIDIOCGUSAGES, HIDIOCSUSAGES commands

commit 93a2001b upstream.

This patch validates the num_values parameter from userland during the
HIDIOCGUSAGES and HIDIOCSUSAGES commands. Previously, if the report id was set
to HID_REPORT_ID_UNKNOWN, we would fail to validate the num_values parameter
leading to a heap overflow.
Signed-off-by: Scott Bauer <sbauer@plzdonthack.me>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/hid/usbhid/hiddev.c

@@ -515,12 +515,12 @@ static noinline int hiddev_ioctl_usage(struct hiddev *hiddev, unsigned int cmd,
 					goto inval;
 			} else if (uref->usage_index >= field->report_count)
 				goto inval;
+		}
 
-			else if ((cmd == HIDIOCGUSAGES || cmd == HIDIOCSUSAGES) &&
+		if ((cmd == HIDIOCGUSAGES || cmd == HIDIOCSUSAGES) &&
 		    (uref_multi->num_values > HID_MAX_MULTI_USAGES ||
 		     uref->usage_index + uref_multi->num_values > field->report_count))
 			goto inval;
-		}
 
 		switch (cmd) {
 		case HIDIOCGUSAGE: