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[PATCH] grub-core/net/arp.c: trim arp packets with abnormal size.


From: Paulo Flabiano Smorigo
Subject: [PATCH] grub-core/net/arp.c: trim arp packets with abnormal size.
Date: Fri, 31 Jan 2014 13:35:11 -0200
User-agent: Mutt/null+5621 (d3096e8796e7) (2012-12-30)

* grub-core/net/arp.c (grub_net_arp_receive): 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.

This is just a fix in time for 2.02. I'm planning to rewrite the arp response 
code
after the release.

diff --git a/ChangeLog b/ChangeLog
index cfa9c83..10e9c3d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2014-01-31  Paulo Flabiano Smorigo  <address@hidden>
+
+       * grub-core/net/arp.c (grub_net_arp_receive): 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.
+
 2014-01-29  Vladimir Serbinenko  <address@hidden>
 
        * grub-core/disk/ahci.c: Increase timeout. Some SSDs take up to
diff --git a/grub-core/net/arp.c b/grub-core/net/arp.c
index d62d0cc..77581f4 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];

-- 
Paulo Flabiano Smorigo
IBM Linux Technology Center




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