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Subject[PATCH 4.9 10/54] l2tp: hold tunnel socket when handling control frames in l2tp_ip and l2tp_ip6
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Guillaume Nault <g.nault@alphalink.fr>


[ Upstream commit 94d7ee0baa8b764cf64ad91ed69464c1a6a0066b ]

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@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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
@@ -178,9 +178,10 @@ 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
@@ -191,9 +191,10 @@ 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 ipv6hdr *iph = ipv6_hdr(skb);

read_lock_bh(&l2tp_ip6_lock);

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