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authorGuillaume Nault <g.nault@alphalink.fr>2017-11-03 16:49:00 +0100
committerDavid S. Miller <davem@davemloft.net>2017-11-05 22:22:15 +0900
commit8f7dc9ae4a7aece9fbc3e6637bdfa38b36bcdf09 (patch)
treef2c6972dbfa0d0d4634370b1575cb57228150633 /net/l2tp/l2tp_ip6.c
parentbaedf68a068ca29624f241426843635920f16e1d (diff)
l2tp: don't use l2tp_tunnel_find() in l2tp_ip and l2tp_ip6
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: 0d76751fad77 ("l2tp: Add L2TPv3 IP encapsulation (no UDP) support") Fixes: a32e0eec7042 ("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>
Diffstat (limited to 'net/l2tp/l2tp_ip6.c')
-rw-r--r--net/l2tp/l2tp_ip6.c24
1 files changed, 9 insertions, 15 deletions
diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
index 88b397c30d86..8bcaa975b432 100644
--- a/net/l2tp/l2tp_ip6.c
+++ b/net/l2tp/l2tp_ip6.c
@@ -136,6 +136,7 @@ static int l2tp_ip6_recv(struct sk_buff *skb)
unsigned char *ptr, *optr;
struct l2tp_session *session;
struct l2tp_tunnel *tunnel = NULL;
+ struct ipv6hdr *iph;
int length;
if (!pskb_may_pull(skb, 4))
@@ -192,24 +193,17 @@ pass_up:
goto discard;
tunnel_id = ntohl(*(__be32 *) &skb->data[4]);
- tunnel = l2tp_tunnel_find(net, tunnel_id);
- if (tunnel) {
- sk = tunnel->sock;
- sock_hold(sk);
- } else {
- struct ipv6hdr *iph = ipv6_hdr(skb);
-
- read_lock_bh(&l2tp_ip6_lock);
- sk = __l2tp_ip6_bind_lookup(net, &iph->daddr, &iph->saddr,
- inet6_iif(skb), tunnel_id);
- if (!sk) {
- read_unlock_bh(&l2tp_ip6_lock);
- goto discard;
- }
+ iph = ipv6_hdr(skb);
- sock_hold(sk);
+ read_lock_bh(&l2tp_ip6_lock);
+ sk = __l2tp_ip6_bind_lookup(net, &iph->daddr, &iph->saddr,
+ inet6_iif(skb), tunnel_id);
+ if (!sk) {
read_unlock_bh(&l2tp_ip6_lock);
+ goto discard;
}
+ sock_hold(sk);
+ read_unlock_bh(&l2tp_ip6_lock);
if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
goto discard_put;