diff options
author | Guillaume Nault <g.nault@alphalink.fr> | 2017-11-03 16:49:00 +0100 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2017-11-05 22:22:15 +0900 |
commit | 8f7dc9ae4a7aece9fbc3e6637bdfa38b36bcdf09 (patch) | |
tree | f2c6972dbfa0d0d4634370b1575cb57228150633 | |
parent | baedf68a068ca29624f241426843635920f16e1d (diff) | |
download | linux-stable-8f7dc9ae4a7aece9fbc3e6637bdfa38b36bcdf09.tar.gz linux-stable-8f7dc9ae4a7aece9fbc3e6637bdfa38b36bcdf09.tar.bz2 linux-stable-8f7dc9ae4a7aece9fbc3e6637bdfa38b36bcdf09.zip |
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>
-rw-r--r-- | net/l2tp/l2tp_ip.c | 24 | ||||
-rw-r--r-- | net/l2tp/l2tp_ip6.c | 24 |
2 files changed, 18 insertions, 30 deletions
diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c index 4d322c1b7233..e4280b6568b4 100644 --- a/net/l2tp/l2tp_ip.c +++ b/net/l2tp/l2tp_ip.c @@ -123,6 +123,7 @@ static int l2tp_ip_recv(struct sk_buff *skb) unsigned char *ptr, *optr; struct l2tp_session *session; struct l2tp_tunnel *tunnel = NULL; + struct iphdr *iph; int length; if (!pskb_may_pull(skb, 4)) @@ -178,24 +179,17 @@ 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 iphdr *iph = (struct iphdr *) skb_network_header(skb); - - read_lock_bh(&l2tp_ip_lock); - sk = __l2tp_ip_bind_lookup(net, iph->daddr, iph->saddr, - inet_iif(skb), tunnel_id); - if (!sk) { - read_unlock_bh(&l2tp_ip_lock); - goto discard; - } + iph = (struct iphdr *)skb_network_header(skb); - sock_hold(sk); + read_lock_bh(&l2tp_ip_lock); + sk = __l2tp_ip_bind_lookup(net, iph->daddr, iph->saddr, inet_iif(skb), + tunnel_id); + if (!sk) { read_unlock_bh(&l2tp_ip_lock); + goto discard; } + sock_hold(sk); + read_unlock_bh(&l2tp_ip_lock); if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb)) goto discard_put; 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; |