[PATCH 1/1] netfilter: h323: avoid potential attack

[Zhouyi Zhou]

From: Zhouyi Zhou <yizhouz...@ict.ac.cn>

I think hackers chould build a malicious h323 packet to overflow
the pointer p which will panic during the memcpy(addr, p, len)

For example, he may fabricate a very large taddr->ipAddress.ip; 

Signed-off-by: Zhouyi Zhou <zhouzho...@gmail.com>
---
 net/netfilter/nf_conntrack_h323_main.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/netfilter/nf_conntrack_h323_main.c 
b/net/netfilter/nf_conntrack_h323_main.c
index 9511af0..3b3dd8c 100644
--- a/net/netfilter/nf_conntrack_h323_main.c
+++ b/net/netfilter/nf_conntrack_h323_main.c
@@ -110,6 +110,10 @@ int (*nat_q931_hook) (struct sk_buff *skb,
 
 static DEFINE_SPINLOCK(nf_h323_lock);
 static char *h323_buffer;
+#define CHECK_BOUND(p, n) do {                                 \
+               if (((p - h323_buffer) + n) > 65536)            \
+                       return 0;                               \
+} while (0)
 
 static struct nf_conntrack_helper nf_conntrack_helper_h245;
 static struct nf_conntrack_helper nf_conntrack_helper_q931[];
@@ -247,6 +251,8 @@ static int get_h245_addr(struct nf_conn *ct, const unsigned 
char *data,
                return 0;
        }
 
+       CHECK_BOUND(p, len);
+
        memcpy(addr, p, len);
        memset((void *)addr + len, 0, sizeof(*addr) - len);
        memcpy(port, p + len, sizeof(__be16));
@@ -669,6 +675,8 @@ int get_h225_addr(struct nf_conn *ct, unsigned char *data,
                return 0;
        }
 
+       CHECK_BOUND(p, len);
+
        memcpy(addr, p, len);
        memset((void *)addr + len, 0, sizeof(*addr) - len);
        memcpy(port, p + len, sizeof(__be16));
-- 
1.7.10.4