From d6a61ec936676dbe25a6eb76e1229787dc2fbba8 Mon Sep 17 00:00:00 2001
From: Guillaume Nault <g.nault@alphalink.fr>
Date: Fri, 10 Aug 2018 13:21:55 +0200
Subject: [PATCH] l2tp: define l2tp_tunnel_uses_xfrm()

Use helper function to figure out if a tunnel is using ipsec.
Also, avoid accessing ->sk_policy directly since it's RCU protected.

Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 net/l2tp/l2tp_core.h    | 19 +++++++++++++++++++
 net/l2tp/l2tp_netlink.c |  7 +------
 net/l2tp/l2tp_ppp.c     |  5 +----
 3 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
index 5804065dfbfb..04a9488c54b4 100644
--- a/net/l2tp/l2tp_core.h
+++ b/net/l2tp/l2tp_core.h
@@ -15,6 +15,10 @@
 #include <net/dst.h>
 #include <net/sock.h>
 
+#ifdef CONFIG_XFRM
+#include <net/xfrm.h>
+#endif
+
 /* Just some random numbers */
 #define L2TP_TUNNEL_MAGIC	0x42114DDA
 #define L2TP_SESSION_MAGIC	0x0C04EB7D
@@ -284,6 +288,21 @@ static inline u32 l2tp_tunnel_dst_mtu(const struct l2tp_tunnel *tunnel)
 	return mtu;
 }
 
+#ifdef CONFIG_XFRM
+static inline bool l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel *tunnel)
+{
+	struct sock *sk = tunnel->sock;
+
+	return sk && (rcu_access_pointer(sk->sk_policy[0]) ||
+		      rcu_access_pointer(sk->sk_policy[1]));
+}
+#else
+static inline bool l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel *tunnel)
+{
+	return false;
+}
+#endif
+
 #define l2tp_printk(ptr, type, func, fmt, ...)				\
 do {									\
 	if (((ptr)->debug) & (type))					\
diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
index 2e1e92651545..357503e5acd5 100644
--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -710,9 +710,6 @@ static int l2tp_nl_session_send(struct sk_buff *skb, u32 portid, u32 seq, int fl
 	void *hdr;
 	struct nlattr *nest;
 	struct l2tp_tunnel *tunnel = session->tunnel;
-	struct sock *sk = NULL;
-
-	sk = tunnel->sock;
 
 	hdr = genlmsg_put(skb, portid, seq, &l2tp_nl_family, flags, cmd);
 	if (!hdr)
@@ -738,10 +735,8 @@ static int l2tp_nl_session_send(struct sk_buff *skb, u32 portid, u32 seq, int fl
 	    nla_put_u8(skb, L2TP_ATTR_RECV_SEQ, session->recv_seq) ||
 	    nla_put_u8(skb, L2TP_ATTR_SEND_SEQ, session->send_seq) ||
 	    nla_put_u8(skb, L2TP_ATTR_LNS_MODE, session->lns_mode) ||
-#ifdef CONFIG_XFRM
-	    (((sk) && (sk->sk_policy[0] || sk->sk_policy[1])) &&
+	    (l2tp_tunnel_uses_xfrm(tunnel) &&
 	     nla_put_u8(skb, L2TP_ATTR_USING_IPSEC, 1)) ||
-#endif
 	    (session->reorder_timeout &&
 	     nla_put_msecs(skb, L2TP_ATTR_RECV_TIMEOUT,
 			   session->reorder_timeout, L2TP_ATTR_PAD)))
diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index 6e2c8e7595e0..c33ef9a3f3b5 100644
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -95,7 +95,6 @@
 #include <net/netns/generic.h>
 #include <net/ip.h>
 #include <net/udp.h>
-#include <net/xfrm.h>
 #include <net/inet_common.h>
 
 #include <asm/byteorder.h>
@@ -1153,9 +1152,7 @@ static int pppol2tp_tunnel_ioctl(struct l2tp_tunnel *tunnel,
 			l2tp_session_dec_refcount(session);
 			break;
 		}
-#ifdef CONFIG_XFRM
-		stats.using_ipsec = (sk->sk_policy[0] || sk->sk_policy[1]) ? 1 : 0;
-#endif
+		stats.using_ipsec = l2tp_tunnel_uses_xfrm(tunnel);
 		pppol2tp_copy_stats(&stats, &tunnel->stats);
 		if (copy_to_user((void __user *) arg, &stats, sizeof(stats))) {
 			err = -EFAULT;
-- 
2.30.2