--- a/netwerk/base/NetworkInfoServiceCocoa.cpp
+++ b/netwerk/base/NetworkInfoServiceCocoa.cpp
@@ -63,17 +63,17 @@ DoListAddresses(AddrMapType& aAddrMap)
     return NS_OK;
 }
 
 static nsresult
 ListInterfaceAddresses(int aFd, const char* aInterface, AddrMapType& aAddrMap)
 {
     struct ifreq ifreq;
     memset(&ifreq, 0, sizeof(struct ifreq));
-    strncpy(ifreq.ifr_name, aInterface, IFNAMSIZ);
+    strncpy(ifreq.ifr_name, aInterface, IFNAMSIZ - 1);
     if (ioctl(aFd, SIOCGIFADDR, &ifreq) != 0) {
         return NS_ERROR_FAILURE;
     }
 
     char host[128];
     int family;
     switch(family=ifreq.ifr_addr.sa_family) {
       case AF_INET:

--- a/netwerk/base/NetworkInfoServiceLinux.cpp
+++ b/netwerk/base/NetworkInfoServiceLinux.cpp
@@ -63,17 +63,17 @@ DoListAddresses(AddrMapType& aAddrMap)
     return NS_OK;
 }
 
 static nsresult
 ListInterfaceAddresses(int aFd, const char* aInterface, AddrMapType& aAddrMap)
 {
     struct ifreq ifreq;
     memset(&ifreq, 0, sizeof(struct ifreq));
-    strncpy(ifreq.ifr_name, aInterface, IFNAMSIZ);
+    strncpy(ifreq.ifr_name, aInterface, IFNAMSIZ - 1);
     if (ioctl(aFd, SIOCGIFADDR, &ifreq) != 0) {
         return NS_ERROR_FAILURE;
     }
 
     char host[128];
     int family;
     switch(family=ifreq.ifr_addr.sa_family) {
       case AF_INET: