[PATCH 4.4 123/230] netfilter: nf_conntrack_tcp: Fix stack out of bounds when parsing TCP options

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxxxxxx>

commit 644c7e48cb59cfc6988ddc7bf3d3b1ba5fe7fa9d upstream.

Baozeng Ding reported a KASAN stack out of bounds issue - it uncovered that
the TCP option parsing routines in netfilter TCP connection tracking could
read one byte out of the buffer of the TCP options.  Therefore in the patch
we check that the available data length is large enough to parse both TCP
option code and size.

Reported-by: Baozeng Ding <sploving1@xxxxxxxxx>
Tested-by: Baozeng Ding <sploving1@xxxxxxxxx>
Signed-off-by: Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Cc: Zubin Mithra <zsm@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 net/netfilter/nf_conntrack_proto_tcp.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/net/netfilter/nf_conntrack_proto_tcp.c
+++ b/net/netfilter/nf_conntrack_proto_tcp.c
@@ -410,6 +410,8 @@ static void tcp_options(const struct sk_
 			length--;
 			continue;
 		default:
+			if (length < 2)
+				return;
 			opsize=*ptr++;
 			if (opsize < 2) /* "silly options" */
 				return;
@@ -470,6 +472,8 @@ static void tcp_sack(const struct sk_buf
 			length--;
 			continue;
 		default:
+			if (length < 2)
+				return;
 			opsize = *ptr++;
 			if (opsize < 2) /* "silly options" */
 				return;