diff mbox

[1/1] net: netfilter: Fix stack out of bounds when parsing TCP options

Message ID 1459330475-2220-2-git-send-email-kadlec@blackhole.kfki.hu
State Accepted
Delegated to: Pablo Neira
Headers show

Commit Message

Jozsef Kadlecsik March 30, 2016, 9:34 a.m. UTC 
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@gmail.com>
Tested-by: Baozeng Ding <sploving1@gmail.com>
Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
---
 net/netfilter/nf_conntrack_proto_tcp.c | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Pablo Neira Ayuso April 7, 2016, 4:43 p.m. UTC | #1 
On Wed, Mar 30, 2016 at 11:34:35AM +0200, Jozsef Kadlecsik wrote:
> 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.

Applied, thanks Jozsef.
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diff mbox

Patch

diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
index 278f3b9..7cc1d9c 100644
--- 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_buff *skb,
 			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_buff *skb, unsigned int dataoff,
 			length--;
 			continue;
 		default:
+			if (length < 2)
+				return;
 			opsize = *ptr++;
 			if (opsize < 2) /* "silly options" */
 				return;