From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Paulo Flabiano Smorigo <pfsmorigo@br.ibm.com>
Date: Wed, 5 Feb 2014 09:42:42 -0200
Subject: [PATCH] trim arp packets with abnormal size

GRUB uses arp request to create the arp response. If the incoming packet
is foobared, GRUB needs to trim the arp response packet before sending it.
---
 grub-core/net/arp.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/grub-core/net/arp.c b/grub-core/net/arp.c
index d62d0cc1e01..77581f4b29a 100644
--- a/grub-core/net/arp.c
+++ b/grub-core/net/arp.c
@@ -162,6 +162,12 @@ grub_net_arp_receive (struct grub_net_buff *nb,
     if (grub_net_addr_cmp (&inf->address, &target_addr) == 0
 	&& grub_be_to_cpu16 (arp_header->op) == ARP_REQUEST)
       {
+        if ((nb->tail - nb->data) > 50)
+          {
+            grub_dprintf ("net", "arp packet with abnormal size (%ld bytes).\n",
+                         nb->tail - nb->data);
+            nb->tail = nb->data + 50;
+          }
 	grub_net_link_level_address_t target;
 	/* We've already checked that pln is either 4 or 16.  */
 	char tmp[16];