netdev - [PATCH net-2.6] ip: NULL pointer dereferrence in tcp_v(4|6)_send

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Message-Id: <1222792151-11861-1-git-send-email-den@openvz.org>
Date:	Tue, 30 Sep 2008 20:29:11 +0400
From:	"Denis V. Lunev" <den@...nvz.org>
To:	davem@...emloft.net
Cc:	xemul@...nvz.org, vgusev@...nvz.org, netdev@...r.kernel.org,
	"Denis V. Lunev" <den@...nvz.org>
Subject: [PATCH net-2.6] ip: NULL pointer dereferrence in tcp_v(4|6)_send_ack

The following actions are possible:
tcp_v4_rcv
  skb->dev = NULL;
  tcp_v4_do_rcv
    tcp_v4_hnd_req
      tcp_check_req
        req->rsk_ops->send_ack == tcp_v4_send_ack

So, skb->dev can be NULL in tcp_v4_send_ack. We must obtain namespace
from dst entry. IPv6 codepath is similar.

Thanks to Vitaliy Gusev <vgusev@...nvz.org> for initial oops decoding.

Signed-off-by: Denis V. Lunev <den@...nvz.org>
---
 net/ipv4/tcp_ipv4.c |    2 +-
 net/ipv6/tcp_ipv6.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 1b4fee2..011478e 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -618,7 +618,7 @@ static void tcp_v4_send_ack(struct sk_buff *skb, u32 seq, u32 ack,
 			];
 	} rep;
 	struct ip_reply_arg arg;
-	struct net *net = dev_net(skb->dev);
+	struct net *net = dev_net(skb->dst->dev);
 
 	memset(&rep.th, 0, sizeof(struct tcphdr));
 	memset(&arg, 0, sizeof(arg));
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index b585c85..10e22fd 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1050,7 +1050,7 @@ static void tcp_v6_send_ack(struct sk_buff *skb, u32 seq, u32 ack, u32 win, u32
 	struct tcphdr *th = tcp_hdr(skb), *t1;
 	struct sk_buff *buff;
 	struct flowi fl;
-	struct net *net = dev_net(skb->dev);
+	struct net *net = dev_net(skb->dst->dev);
 	struct sock *ctl_sk = net->ipv6.tcp_sk;
 	unsigned int tot_len = sizeof(struct tcphdr);
 	__be32 *topt;
-- 
1.5.6.4

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