This is a note to let you know that I've just added the patch titled
l2tp: don't use l2tp_tunnel_find() in l2tp_ip and l2tp_ip6
to the 4.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
l2tp-don-t-use-l2tp_tunnel_find-in-l2tp_ip-and-l2tp_ip6.patch
and it can be found in the queue-4.13 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Tue Nov 21 13:07:20 CET 2017
From: Guillaume Nault <g.nault@xxxxxxxxxxxx>
Date: Fri, 3 Nov 2017 16:49:00 +0100
Subject: l2tp: don't use l2tp_tunnel_find() in l2tp_ip and l2tp_ip6
From: Guillaume Nault <g.nault@xxxxxxxxxxxx>
[ Upstream commit 8f7dc9ae4a7aece9fbc3e6637bdfa38b36bcdf09 ]
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@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/l2tp/l2tp_ip.c | 24 +++++++++---------------
net/l2tp/l2tp_ip6.c | 24 +++++++++---------------
2 files changed, 18 insertions(+), 30 deletions(-)
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -123,6 +123,7 @@ static int l2tp_ip_recv(struct sk_buff *
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;
--- a/net/l2tp/l2tp_ip6.c
+++ b/net/l2tp/l2tp_ip6.c
@@ -136,6 +136,7 @@ static int l2tp_ip6_recv(struct sk_buff
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;
Patches currently in stable-queue which might be from g.nault@xxxxxxxxxxxx are
queue-4.13/l2tp-don-t-use-l2tp_tunnel_find-in-l2tp_ip-and-l2tp_ip6.patch