From: Guillaume Nault <g.nault@alphalink.fr>
Date: Tue, 29 Nov 2016 12:09:45 +0000 (+0100)
Subject: l2tp: hold socket before dropping lock in l2tp_ip{, 6}_recv()
X-Git-Tag: v4.9-rc8~5^2~29^2~3
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=a3c18422a4b4e108bcf6a2328f48867e1003fd95;p=linux.git

l2tp: hold socket before dropping lock in l2tp_ip{, 6}_recv()

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.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
index 1f57094d3111..4d1c942cc91b 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 af9abfff637c..e3fc7786f188 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;