time: Validate user input in compat_settimeofday()

The user value is validated after converting the timeval to a timespec, but
for a wide range of negative tv_usec values the multiplication overflow turns
them in positive numbers. So the 'validated later' is not catching the
invalid input.
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/1562460701-113301-1-git-send-email-zhengbin13@huawei.com

kernel/time/time.c

@@ -251,6 +251,10 @@ COMPAT_SYSCALL_DEFINE2(settimeofday, struct old_timeval32 __user *, tv,
 	if (tv) {
 		if (compat_get_timeval(&user_tv, tv))
 			return -EFAULT;
+
+		if (!timeval_valid(&user_tv))
+			return -EINVAL;
+
 		new_ts.tv_sec = user_tv.tv_sec;
 		new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
 	}