grub2/0476-trim-arp-packets-with-abnormal-size.patch

From ee4302aa644523afd447e21201412ab6da00d4d6 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 476/506] 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 4b68c41..f7c59d3 100644
--- a/grub-core/net/arp.c
+++ b/grub-core/net/arp.c
@@ -142,6 +142,12 @@ grub_net_arp_receive (struct grub_net_buff *nb,
     if (grub_net_addr_cmp (&inf->address, &target_addr) == 0
 	&& arp_packet->op == grub_cpu_to_be16_compile_time (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;
 	struct grub_net_buff nb_reply;
 	struct arppkt *arp_reply;
-- 
2.4.3