This is a note to let you know that I've just added the patch titled l2tp: hold tunnel socket when handling control frames in l2tp_ip and l2tp_ip6 to the 4.4-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-hold-tunnel-socket-when-handling-control-frames-in-l2tp_ip-and-l2tp_ip6.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 94d7ee0baa8b764cf64ad91ed69464c1a6a0066b Mon Sep 17 00:00:00 2001 From: Guillaume Nault <g.nault@xxxxxxxxxxxx> Date: Wed, 29 Mar 2017 08:44:59 +0200 Subject: l2tp: hold tunnel socket when handling control frames in l2tp_ip and l2tp_ip6 From: Guillaume Nault <g.nault@xxxxxxxxxxxx> commit 94d7ee0baa8b764cf64ad91ed69464c1a6a0066b upstream. The code following l2tp_tunnel_find() expects that a new reference is held on sk. Either sk_receive_skb() or the discard_put error path will drop a reference from the tunnel's socket. This issue exists in both l2tp_ip and l2tp_ip6. Fixes: a3c18422a4b4 ("l2tp: hold socket before dropping lock in l2tp_ip{, 6}_recv()") 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 | 5 +++-- net/l2tp/l2tp_ip6.c | 5 +++-- 2 files changed, 6 insertions(+), 4 deletions(-) --- a/net/l2tp/l2tp_ip.c +++ b/net/l2tp/l2tp_ip.c @@ -177,9 +177,10 @@ pass_up: tunnel_id = ntohl(*(__be32 *) &skb->data[4]); tunnel = l2tp_tunnel_find(net, tunnel_id); - if (tunnel != NULL) + if (tunnel) { sk = tunnel->sock; - else { + sock_hold(sk); + } else { struct iphdr *iph = (struct iphdr *) skb_network_header(skb); read_lock_bh(&l2tp_ip_lock); --- a/net/l2tp/l2tp_ip6.c +++ b/net/l2tp/l2tp_ip6.c @@ -188,9 +188,10 @@ pass_up: tunnel_id = ntohl(*(__be32 *) &skb->data[4]); tunnel = l2tp_tunnel_find(&init_net, tunnel_id); - if (tunnel != NULL) + if (tunnel) { sk = tunnel->sock; - else { + sock_hold(sk); + } else { struct ipv6hdr *iph = ipv6_hdr(skb); read_lock_bh(&l2tp_ip6_lock); Patches currently in stable-queue which might be from g.nault@xxxxxxxxxxxx are queue-4.4/l2tp-hold-socket-before-dropping-lock-in-l2tp_ip-6-_.patch queue-4.4/l2tp-hold-tunnel-socket-when-handling-control-frames-in-l2tp_ip-and-l2tp_ip6.patch