xfrm: policy: init locks early

commit c282222a upstream.

Dmitry reports following splat:
 INFO: trying to register non-static key.
 the code is fine but needs lockdep annotation.
 turning off the locking correctness validator.
 CPU: 0 PID: 13059 Comm: syz-executor1 Not tainted 4.10.0-rc7-next-20170207 #1
[..]
 spin_lock_bh include/linux/spinlock.h:304 [inline]
 xfrm_policy_flush+0x32/0x470 net/xfrm/xfrm_policy.c:963
 xfrm_policy_fini+0xbf/0x560 net/xfrm/xfrm_policy.c:3041
 xfrm_net_init+0x79f/0x9e0 net/xfrm/xfrm_policy.c:3091
 ops_init+0x10a/0x530 net/core/net_namespace.c:115
 setup_net+0x2ed/0x690 net/core/net_namespace.c:291
 copy_net_ns+0x26c/0x530 net/core/net_namespace.c:396
 create_new_namespaces+0x409/0x860 kernel/nsproxy.c:106
 unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:205
 SYSC_unshare kernel/fork.c:2281 [inline]

Problem is that when we get error during xfrm_net_init we will call
xfrm_policy_fini which will acquire xfrm_policy_lock before it was
initialized.  Just move it around so locks get set up first.
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Fixes: 283bc9f3 ("xfrm: Namespacify xfrm state/policy locks")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
[bwh: Backported to 3.2: xfrm_policy_lock is an rwlock]

net/xfrm/xfrm_policy.c

@@ -2878,6 +2878,11 @@ static int __net_init xfrm_net_init(struct net *net)
 {
 	int rv;
 
+	/* Initialize the per-net locks here */
+	spin_lock_init(&net->xfrm.xfrm_state_lock);
+	rwlock_init(&net->xfrm.xfrm_policy_lock);
+	mutex_init(&net->xfrm.xfrm_cfg_mutex);
+
 	rv = xfrm_statistics_init(net);
 	if (rv < 0)
 		goto out_statistics;
@@ -2894,11 +2899,6 @@ static int __net_init xfrm_net_init(struct net *net)
 	if (rv < 0)
 		goto out;
 
-	/* Initialize the per-net locks here */
-	spin_lock_init(&net->xfrm.xfrm_state_lock);
-	rwlock_init(&net->xfrm.xfrm_policy_lock);
-	mutex_init(&net->xfrm.xfrm_cfg_mutex);
-
 	return 0;
 
 out: