From: Willem de Bruijn <willemb@google.com>
Date: Thu, 10 Mar 2016 02:58:33 +0000 (-0500)
Subject: ax25: add link layer header validation function
X-Git-Tag: v3.2.80~11
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=0954b59d9f4b2dcc59f28d1f64c3a21062a64372;hp=b5518429e70cd783b8ca52335456172c1a0589f6;ds=sidebyside

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 cf0c47a26530..a0c9956b5b23 100644
--- 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
 
+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,
+	.validate = ax25_validate_header,
 };
 
 EXPORT_SYMBOL(ax25_hard_header);