only write to the watchdog if the fd is valid

Signed-off-by: John Crispin <blogic@openwrt.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/watchdog.c b/watchdog.c
index 3c097e2..592ae7e 100644
--- a/watchdog.c
+++ b/watchdog.c
@@ -35,7 +35,7 @@ static int wdt_frequency = 5;
 void watchdog_ping(void)
 {
 	DEBUG(4, "Ping\n");
-	if (write(wdt_fd, "X", 1) < 0)
+	if (wdt_fd >= 0 && write(wdt_fd, "X", 1) < 0)
 		ERROR("WDT failed to write: %s\n", strerror(errno));
 }