Check timer period and timeout arguments

The uev_timer_init() and uev_timer_set() functions allow timeout and
period to be set < 0, which is not supported.  This patch adds a very
simple range check.

Signed-off-by: Joachim Nilsson <joachim.nilsson@westermo.se>

timer.c

@@ -67,6 +67,11 @@ int uev_timer_init(uev_ctx_t *ctx, uev_t *w, uev_cb_t *cb, void *arg, int timeou
 {
 	int fd;
 
+	if (timeout < 0 || period < 0) {
+		errno = ERANGE;
+		return -1;
+	}
+
 	fd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK | TFD_CLOEXEC);
 	if (fd < 0)
 		return -1;
@@ -100,6 +105,11 @@ int uev_timer_set(uev_t *w, int timeout, int period)
 		return -1;
 	}
 
+	if (timeout < 0 || period < 0) {
+		errno = ERANGE;
+		return -1;
+	}
+
 	/* Handle stopped timers */
 	if (w->fd < 0) {
 		/* Timer already stopped */