l2tp: don't use l2tp_tunnel_find() in l2tp_ip and l2tp_ip6
commit 8f7dc9ae4a7aece9fbc3e6637bdfa38b36bcdf09 upstream. Using l2tp_tunnel_find() in l2tp_ip_recv() is wrong for two reasons: * It doesn't take a reference on the returned tunnel, which makes the call racy wrt. concurrent tunnel deletion. * The lookup is only based on the tunnel identifier, so it can return a tunnel that doesn't match the packet's addresses or protocol. For example, a packet sent to an L2TPv3 over IPv6 tunnel can be delivered to an L2TPv2 over UDPv4 tunnel. This is worse than a simple cross-talk: when delivering the packet to an L2TP over UDP tunnel, the corresponding socket is UDP, where ->sk_backlog_rcv() is NULL. Calling sk_receive_skb() will then crash the kernel by trying to execute this callback. And l2tp_tunnel_find() isn't even needed here. __l2tp_ip_bind_lookup() properly checks the socket binding and connection settings. It was used as a fallback mechanism for finding tunnels that didn't have their data path registered yet. But it's not limited to this case and can be used to replace l2tp_tunnel_find() in the general case. Fix l2tp_ip6 in the same way. Fixes:0d76751fad
("l2tp: Add L2TPv3 IP encapsulation (no UDP) support") Fixes:a32e0eec70
("l2tp: introduce L2TPv3 IP encapsulation support for IPv6") Signed-off-by: Guillaume Nault <g.nault@alphalink.fr> Signed-off-by: David S. Miller <davem@davemloft.net> [bwh: Backported to 3.16: - In l2tp_ip6.c, always look up in init_net - Adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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@ -122,6 +122,7 @@ static int l2tp_ip_recv(struct sk_buff *skb)
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unsigned char *ptr, *optr;
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struct l2tp_session *session;
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struct l2tp_tunnel *tunnel = NULL;
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struct iphdr *iph;
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int length;
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if (!pskb_may_pull(skb, 4))
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@ -177,23 +178,16 @@ pass_up:
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goto discard;
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tunnel_id = ntohl(*(__be32 *) &skb->data[4]);
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tunnel = l2tp_tunnel_find(net, tunnel_id);
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if (tunnel) {
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sk = tunnel->sock;
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sock_hold(sk);
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} else {
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struct iphdr *iph = (struct iphdr *) skb_network_header(skb);
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iph = (struct iphdr *)skb_network_header(skb);
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read_lock_bh(&l2tp_ip_lock);
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sk = __l2tp_ip_bind_lookup(net, iph->daddr, 0, tunnel_id);
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if (!sk) {
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read_unlock_bh(&l2tp_ip_lock);
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goto discard;
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}
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sock_hold(sk);
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read_lock_bh(&l2tp_ip_lock);
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sk = __l2tp_ip_bind_lookup(net, iph->daddr, 0, tunnel_id);
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if (!sk) {
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read_unlock_bh(&l2tp_ip_lock);
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goto discard;
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}
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sock_hold(sk);
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read_unlock_bh(&l2tp_ip_lock);
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if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
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goto discard_put;
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@ -133,6 +133,7 @@ static int l2tp_ip6_recv(struct sk_buff *skb)
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unsigned char *ptr, *optr;
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struct l2tp_session *session;
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struct l2tp_tunnel *tunnel = NULL;
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struct ipv6hdr *iph;
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int length;
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if (!pskb_may_pull(skb, 4))
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@ -189,24 +190,16 @@ pass_up:
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goto discard;
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tunnel_id = ntohl(*(__be32 *) &skb->data[4]);
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tunnel = l2tp_tunnel_find(&init_net, tunnel_id);
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if (tunnel) {
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sk = tunnel->sock;
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sock_hold(sk);
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} else {
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struct ipv6hdr *iph = ipv6_hdr(skb);
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iph = ipv6_hdr(skb);
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read_lock_bh(&l2tp_ip6_lock);
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sk = __l2tp_ip6_bind_lookup(&init_net, &iph->daddr,
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0, tunnel_id);
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if (!sk) {
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read_unlock_bh(&l2tp_ip6_lock);
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goto discard;
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}
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sock_hold(sk);
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read_lock_bh(&l2tp_ip6_lock);
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sk = __l2tp_ip6_bind_lookup(&init_net, &iph->daddr, 0, tunnel_id);
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if (!sk) {
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read_unlock_bh(&l2tp_ip6_lock);
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goto discard;
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}
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sock_hold(sk);
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read_unlock_bh(&l2tp_ip6_lock);
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if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
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goto discard_put;
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