diff --git a/grub-core/net/arp.c b/grub-core/net/arp.c
index 0644d3d2e..6fc7554cd 100644
--- a/grub-core/net/arp.c
+++ b/grub-core/net/arp.c
@@ -39,6 +39,7 @@ grub_net_arp_resolve (struct grub_net_network_level_interface *inf,
   struct arphdr *arp_header;
   grub_net_link_level_address_t target_hw_addr;
   char *aux, arp_data[128];
+  grub_err_t err;
   int i;
 
   /* Check cache table.  */
@@ -52,9 +53,11 @@ grub_net_arp_resolve (struct grub_net_network_level_interface *inf,
   nb.head = arp_data;
   nb.end = arp_data + sizeof (arp_data);
   grub_netbuff_clear (&nb);
-
   grub_netbuff_reserve (&nb, 128);
-  grub_netbuff_push (&nb, sizeof (*arp_header) + 2 * (6 + 4));
+
+  if ((err = grub_netbuff_push (&nb, sizeof (*arp_header) + 2 * (6 + 4))) != GRUB_ERR_NONE)
+    return err;
+
   arp_header = (struct arphdr *) nb.data;
   arp_header->hrd = grub_cpu_to_be16 (GRUB_NET_ARPHRD_ETHERNET);
   arp_header->pro = grub_cpu_to_be16 (GRUB_NET_ETHERTYPE_IP);
diff --git a/grub-core/net/drivers/ieee1275/ofnet.c b/grub-core/net/drivers/ieee1275/ofnet.c
index 9789f2261..2c264edb1 100644
--- a/grub-core/net/drivers/ieee1275/ofnet.c
+++ b/grub-core/net/drivers/ieee1275/ofnet.c
@@ -228,7 +228,10 @@ GRUB_MOD_FINI(ofnet)
   struct grub_net_card *card;
   FOR_NET_CARDS (card) 
     if (card->driver && !grub_strcmp (card->driver->name, "ofnet"))
-      card->driver->fini (card);
+      {
+	card->driver->fini (card);
+	card->driver = NULL;
+      }
   grub_net_card_driver_unregister (&ofdriver);
   grub_getbootp = NULL;
 }
diff --git a/grub-core/net/ethernet.c b/grub-core/net/ethernet.c
index d29193afe..d33a07010 100644
--- a/grub-core/net/ethernet.c
+++ b/grub-core/net/ethernet.c
@@ -15,8 +15,10 @@ send_ethernet_packet (struct grub_net_network_level_interface *inf,
 		      grub_uint16_t ethertype)
 {
   struct etherhdr *eth;
+  grub_err_t err;
 
-  grub_netbuff_push (nb, sizeof (*eth));
+  if ((err = grub_netbuff_push (nb, sizeof (*eth))) != GRUB_ERR_NONE)
+    return err;
   eth = (struct etherhdr *) nb->data;
   grub_memcpy (eth->dst, target_addr.mac, 6);
   grub_memcpy (eth->src, inf->hwaddress.mac, 6);
@@ -33,10 +35,12 @@ grub_net_recv_ethernet_packet (struct grub_net_buff *nb)
   struct llchdr *llch;
   struct snaphdr *snaph;
   grub_uint16_t type;
+  grub_err_t err;
 
   eth = (struct etherhdr *) nb->data;
   type = grub_be_to_cpu16 (eth->type);
-  grub_netbuff_pull (nb, sizeof (*eth));
+  if ((err = grub_netbuff_pull (nb, sizeof (*eth))) != GRUB_ERR_NONE)
+    return err;
 
   if (type <= 1500)
     {
@@ -45,7 +49,8 @@ grub_net_recv_ethernet_packet (struct grub_net_buff *nb)
 
       if (llch->dsap == 0xaa && llch->ssap == 0xaa && llch->ctrl == 0x3)
 	{
-	  grub_netbuff_pull (nb, sizeof (*llch));
+	  if ((err = grub_netbuff_pull (nb, sizeof (*llch))) != GRUB_ERR_NONE)
+	    return err;
 	  snaph = (struct snaphdr *) nb->data;
 	  type = snaph->type;
 	}
diff --git a/grub-core/net/ip.c b/grub-core/net/ip.c
index 4adc2b028..749b41d02 100644
--- a/grub-core/net/ip.c
+++ b/grub-core/net/ip.c
@@ -85,7 +85,10 @@ grub_err_t
 grub_net_recv_ip_packets (struct grub_net_buff *nb)
 {
   struct iphdr *iph = (struct iphdr *) nb->data;
-  grub_netbuff_pull (nb, sizeof (*iph));
+  grub_err_t err;
+
+  if ((err = grub_netbuff_pull (nb, sizeof (*iph))) != GRUB_ERR_NONE)
+    return err;
 
   switch (iph->protocol)
     {
diff --git a/grub-core/net/netbuff.c b/grub-core/net/netbuff.c
index aae2f4d8f..d20104ab0 100644
--- a/grub-core/net/netbuff.c
+++ b/grub-core/net/netbuff.c
@@ -95,12 +95,12 @@ grub_err_t
 grub_netbuff_free (struct grub_net_buff *nb)
 {
   grub_free (nb->head);
-  return 0;
+  return GRUB_ERR_NONE;
 }
 
 grub_err_t
 grub_netbuff_clear (struct grub_net_buff *nb)
 {
   nb->data = nb->tail = nb->head;
-  return 0;
+  return GRUB_ERR_NONE;
 }
diff --git a/grub-core/net/tftp.c b/grub-core/net/tftp.c
index ac3b3e9db..138020b08 100644
--- a/grub-core/net/tftp.c
+++ b/grub-core/net/tftp.c
@@ -34,7 +34,8 @@ tftp_open (struct grub_file *file, const char *filename)
   grub_netbuff_clear (&nb);
 
   grub_netbuff_reserve (&nb, 1500);
-  grub_netbuff_push (&nb, sizeof (*tftph));
+  if ((err = grub_netbuff_push (&nb, sizeof (*tftph))) != GRUB_ERR_NONE)
+    return err;
 
   tftph = (struct tftphdr *) nb.data;
 
@@ -67,8 +68,8 @@ tftp_open (struct grub_file *file, const char *filename)
   rrq += grub_strlen ("0") + 1;
   hdrlen = sizeof (tftph->opcode) + rrqlen;
 
-  grub_netbuff_unput (&nb, nb.tail - (nb.data + hdrlen));
-
+  if ((err = grub_netbuff_unput (&nb, nb.tail - (nb.data + hdrlen))) != GRUB_ERR_NONE)
+    return err;
   file->device->net->socket->out_port = TFTP_SERVER_PORT;
 
   err = grub_net_send_udp_packet (file->device->net->socket, &nb);
@@ -130,9 +131,9 @@ tftp_receive (grub_net_socket_t sock, struct grub_net_buff *nb)
       grub_netbuff_clear (nb);
       break;
     case TFTP_DATA:
-      grub_netbuff_pull (nb, sizeof (tftph->opcode) +
-			 sizeof (tftph->u.data.block));
-
+      if ((err = grub_netbuff_pull (nb, sizeof (tftph->opcode) +
+			 sizeof (tftph->u.data.block))) != GRUB_ERR_NONE)
+	return err;
       if (grub_be_to_cpu16 (tftph->u.data.block) == data->block + 1)
 	{
 	  data->block++;
@@ -141,7 +142,8 @@ tftp_receive (grub_net_socket_t sock, struct grub_net_buff *nb)
 	    sock->status = 2;
 	  /* Prevent garbage in broken cards.  */
 	  if (size > 1024)
-	    grub_netbuff_unput (nb, size - 1024);
+	    if ((err = grub_netbuff_unput (nb, size - 1024)) != GRUB_ERR_NONE)
+	      return err;
 	}
       else
 	grub_netbuff_clear (nb);
@@ -154,8 +156,9 @@ tftp_receive (grub_net_socket_t sock, struct grub_net_buff *nb)
     }
   grub_netbuff_clear (&nb_ack);
   grub_netbuff_reserve (&nb_ack, 128);
-  grub_netbuff_push (&nb_ack, sizeof (tftph->opcode) 
-		    + sizeof (tftph->u.ack.block));
+  if ((err = grub_netbuff_push (&nb_ack, sizeof (tftph->opcode) 
+		    + sizeof (tftph->u.ack.block))) != GRUB_ERR_NONE)
+    return err;
 
   tftph = (struct tftphdr *) nb_ack.data;
   tftph->opcode = grub_cpu_to_be16 (TFTP_ACK);
diff --git a/grub-core/net/udp.c b/grub-core/net/udp.c
index 86220bf0f..b070cbb64 100644
--- a/grub-core/net/udp.c
+++ b/grub-core/net/udp.c
@@ -9,8 +9,10 @@ grub_net_send_udp_packet (const grub_net_socket_t socket,
 			  struct grub_net_buff *nb)
 {
   struct udphdr *udph;
+  grub_err_t err;
 
-  grub_netbuff_push (nb, sizeof (*udph));
+  if ((err = grub_netbuff_push (nb, sizeof (*udph))) != GRUB_ERR_NONE)
+    return err;
 
   udph = (struct udphdr *) nb->data;
   udph->src = grub_cpu_to_be16 (socket->in_port);