syscall: msg: validate iovec array itself as well as the buffers it points to

syscall/log.c

@@ -4,6 +4,6 @@
 kern_status_t sys_kern_log(const char *s)
 {
 	struct task *task = current_task();
-	printk("%s: %s", task->t_name, task->t_id, s);
+	printk("%s[%d]: %s", task->t_name, task->t_id, s);
 	return KERN_OK;
 }

syscall/msg.c

@@ -165,6 +165,10 @@ static bool validate_iovec(
 	size_t count,
 	bool rw)
 {
+	if (!validate_access_r(task, iov, count * sizeof(struct iovec))) {
+		return false;
+	}
+
 	for (size_t i = 0; i < count; i++) {
 		bool ok = false;
 		const struct iovec *vec = &iov[i];