[PATCH net 2/5] l2tp: hold socket before dropping lock in l2tp_ip{,6}_recv()

[Guillaume Nault]

Socket must be held while under the protection of the l2tp lock; there
is no guarantee that sk remains valid after the read_unlock_bh() call.

Same issue for l2tp_ip and l2tp_ip6.

Signed-off-by: Guillaume Nault <g.na...@alphalink.fr>
---
 net/l2tp/l2tp_ip.c  | 11 ++++++-----
 net/l2tp/l2tp_ip6.c | 11 ++++++-----
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
index 1f57094..4d1c942 100644
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -183,14 +183,15 @@ static int l2tp_ip_recv(struct sk_buff *skb)
 
                read_lock_bh(&l2tp_ip_lock);
                sk = __l2tp_ip_bind_lookup(net, iph->daddr, 0, tunnel_id);
+               if (!sk) {
+                       read_unlock_bh(&l2tp_ip_lock);
+                       goto discard;
+               }
+
+               sock_hold(sk);
                read_unlock_bh(&l2tp_ip_lock);
        }
 
-       if (sk == NULL)
-               goto discard;
-
-       sock_hold(sk);
-
        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 af9abff..e3fc778 100644
--- a/net/l2tp/l2tp_ip6.c
+++ b/net/l2tp/l2tp_ip6.c
@@ -198,14 +198,15 @@ static int l2tp_ip6_recv(struct sk_buff *skb)
                read_lock_bh(&l2tp_ip6_lock);
                sk = __l2tp_ip6_bind_lookup(net, &iph->daddr,
                                            0, tunnel_id);
+               if (!sk) {
+                       read_unlock_bh(&l2tp_ip6_lock);
+                       goto discard;
+               }
+
+               sock_hold(sk);
                read_unlock_bh(&l2tp_ip6_lock);
        }
 
-       if (sk == NULL)
-               goto discard;
-
-       sock_hold(sk);
-
        if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
                goto discard_put;
 
-- 
2.10.2