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From: Cong Wang <xiyou.wangcong@gmail.com>
To: Andrey Konovalov <andreyknvl@google.com>
Cc: "David S. Miller" <davem@davemloft.net>,
	Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
	James Morris <jmorris@namei.org>,
	Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
	Patrick McHardy <kaber@trash.net>,
	netdev <netdev@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Eric Dumazet <edumazet@google.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	Kostya Serebryany <kcc@google.com>,
	syzkaller <syzkaller@googlegroups.com>
Subject: Re: net/ipv6: slab-out-of-bounds in ip6_tnl_xmit
Date: Mon, 24 Apr 2017 22:04:04 -0700	[thread overview]
Message-ID: <CAM_iQpWnPgn0+-y34nGTB0byonLWCdf3_VAKcH8tK5fdzF4CBg@mail.gmail.com> (raw)
In-Reply-To: <CAM_iQpXLHx=NhSNYU_o4F_V6nNXUHGBSdV=QQnML0B+HD7MbBQ@mail.gmail.com>

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On Mon, Apr 24, 2017 at 9:47 AM, Cong Wang <xiyou.wangcong@gmail.com> wrote:
>
> We use ipv4 dst in ip6_tunnel and cast an IPv4 neigh key as an
> IPv6 address...
>
>
>                 neigh = dst_neigh_lookup(skb_dst(skb),
>                                          &ipv6_hdr(skb)->daddr);
>                 if (!neigh)
>                         goto tx_err_link_failure;
>
>                 addr6 = (struct in6_addr *)&neigh->primary_key; // <=== HERE
>                 addr_type = ipv6_addr_type(addr6);
>
>                 if (addr_type == IPV6_ADDR_ANY)
>                         addr6 = &ipv6_hdr(skb)->daddr;
>
>                 memcpy(&fl6->daddr, addr6, sizeof(fl6->daddr));
>
> Also the network header of the skb at this point should be still IPv4?

Please try the attached patch.

I am not sure how we could handle 4in6 case better than just relying on
the config of ip6 tunnel.

[-- Attachment #2: ip6_tunnel.diff --]
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diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 75fac93..a9692ec 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -1037,7 +1037,7 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,
 	struct ip6_tnl *t = netdev_priv(dev);
 	struct net *net = t->net;
 	struct net_device_stats *stats = &t->dev->stats;
-	struct ipv6hdr *ipv6h = ipv6_hdr(skb);
+	struct ipv6hdr *ipv6h;
 	struct ipv6_tel_txoption opt;
 	struct dst_entry *dst = NULL, *ndst = NULL;
 	struct net_device *tdev;
@@ -1057,26 +1057,28 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,
 
 	/* NBMA tunnel */
 	if (ipv6_addr_any(&t->parms.raddr)) {
-		struct in6_addr *addr6;
-		struct neighbour *neigh;
-		int addr_type;
+		if (skb->protocol == htons(ETH_P_IPV6)) {
+			struct in6_addr *addr6;
+			struct neighbour *neigh;
+			int addr_type;
 
-		if (!skb_dst(skb))
-			goto tx_err_link_failure;
+			if (!skb_dst(skb))
+				goto tx_err_link_failure;
 
-		neigh = dst_neigh_lookup(skb_dst(skb),
-					 &ipv6_hdr(skb)->daddr);
-		if (!neigh)
-			goto tx_err_link_failure;
+			neigh = dst_neigh_lookup(skb_dst(skb),
+						 &ipv6_hdr(skb)->daddr);
+			if (!neigh)
+				goto tx_err_link_failure;
 
-		addr6 = (struct in6_addr *)&neigh->primary_key;
-		addr_type = ipv6_addr_type(addr6);
+			addr6 = (struct in6_addr *)&neigh->primary_key;
+			addr_type = ipv6_addr_type(addr6);
 
-		if (addr_type == IPV6_ADDR_ANY)
-			addr6 = &ipv6_hdr(skb)->daddr;
+			if (addr_type == IPV6_ADDR_ANY)
+				addr6 = &ipv6_hdr(skb)->daddr;
 
-		memcpy(&fl6->daddr, addr6, sizeof(fl6->daddr));
-		neigh_release(neigh);
+			memcpy(&fl6->daddr, addr6, sizeof(fl6->daddr));
+			neigh_release(neigh);
+		}
 	} else if (!(t->parms.flags &
 		     (IP6_TNL_F_USE_ORIG_TCLASS | IP6_TNL_F_USE_ORIG_FWMARK))) {
 		/* enable the cache only only if the routing decision does

  reply	other threads:[~2017-04-25  5:04 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-24 15:03 net/ipv6: slab-out-of-bounds in ip6_tnl_xmit Andrey Konovalov
2017-04-24 16:24 ` Andrey Konovalov
2017-04-24 16:47 ` Cong Wang
2017-04-25  5:04   ` Cong Wang [this message]
2017-04-25 12:32     ` Andrey Konovalov

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