ax25: add link layer header validation function

[ Upstream commit ea47781c26510e5d97f80f9aceafe9065bd5e3aa ]

As variable length protocol, AX25 fails link layer header validation
tests based on a minimum length. header_ops.validate allows protocols
to validate headers that are shorter than hard_header_len. Implement
this callback for AX25.

See also http://comments.gmane.org/gmane.linux.network/401064

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/ax25/ax25_ip.c b/net/ax25/ax25_ip.c
index cf0c47a..a0c9956 100644 (file)
--- a/net/ax25/ax25_ip.c
+++ b/net/ax25/ax25_ip.c
@@ -232,9 +232,24 @@ int ax25_rebuild_header(struct sk_buff *skb)
 
 #endif
 
 
 #endif
 

+static bool ax25_validate_header(const char *header, unsigned int len)
+{
+       ax25_digi digi;
+
+       if (!len)
+               return false;
+
+       if (header[0])
+               return true;
+
+       return ax25_addr_parse(header + 1, len - 1, NULL, NULL, &digi, NULL,
+                              NULL);
+}
+

 const struct header_ops ax25_header_ops = {
        .create = ax25_hard_header,
        .rebuild = ax25_rebuild_header,
 const struct header_ops ax25_header_ops = {
        .create = ax25_hard_header,
        .rebuild = ax25_rebuild_header,

+       .validate = ax25_validate_header,

 };
 
 EXPORT_SYMBOL(ax25_hard_header);
 };
 
 EXPORT_SYMBOL(ax25_hard_header);