Merge branch 'ipv6-blackhole-route-fix'

Martin KaFai Lau says:

====================
ipv6: Initialize rt6_info properly in ip6_blackhole_route()

This patchset ensures the rt6_info's fields are initialized properly
in ip6_blackhole_route() where xfrm_policy is the primarily user.
The first patch is a prep work.  The second patch is the fix.  It
fixes d52d3997 ("ipv6: Create percpu rt6_info").

Here is the oops reported by Phil Sutter <phil@nwl.cc>:

BUG: unable to handle kernel NULL pointer dereference at 00000000000000a0
IP: [<ffffffff8171a95e>] __ip6_datagram_connect+0x71e/0xa20
PGD c2cb1067 PUD c2d7a067 PMD 0
Oops: 0000 [#1] PREEMPT SMP
Modules linked in: cmac nfs lockd grace sunrpc bridge stp llc nvidia(PO) snd_usb_audio snd_usbmidi_lib iTCO_wdt
CPU: 1 PID: 2964 Comm: ping6 Tainted: P           O    4.2.1-aufs #10
Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./4Core1333-Viiv, BIOS P1.60 07/01/2008
task: ffff8800ca62bc00 ti: ffff880129a14000 task.ti: ffff880129a14000
RIP: 0010:[<ffffffff8171a95e>]  [<ffffffff8171a95e>] __ip6_datagram_connect+0x71e/0xa20
RSP: 0018:ffff880129a17da8  EFLAGS: 00010296
RAX: 000000000000000b RBX: 0000000000000000 RCX: 0000000000000006
RDX: 0000000000000007 RSI: 0000000000000246 RDI: ffff88012fc8d5a0
RBP: ffff8800cb9a9048 R08: 756e207369207472 R09: 216c6c756e207369
R10: 0000000000000665 R11: 0000000000000006 R12: ffff8800cb9a8cf8
R13: ffff8800cb9a8cf8 R14: 0000000000000000 R15: ffff8800cb9a8cc0
FS:  00007fb76ad74700(0000) GS:ffff88012fc80000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000000000a0 CR3: 00000000c2dba000 CR4: 00000000000406e0
Stack:
 ffff8800cb9a9048 ffff8800cb9a8de0 ffff8800cb9feb70 ffffffff816b2c41
 00007fb70000000b ffffea0000df7200 ffff8800cb9f5cfc ffff8800cb9a8cc0
 03fffffffe068a20 ffff8800cb9a8cc0 ffffffff817097c0 0000000100000000
Call Trace:
 [<ffffffff816b2c41>] ? udp_lib_get_port+0x1a1/0x380
 [<ffffffff817097c0>] ? udpv6_rcv+0x20/0x20
 [<ffffffff8171ac82>] ? ip6_datagram_connect+0x22/0x40
 [<ffffffff8163ae9b>] ? SyS_connect+0x6b/0xb0
 [<ffffffff810767ac>] ? __do_page_fault+0x15c/0x380
 [<ffffffff8163a8d3>] ? SyS_socket+0x63/0xa0
 [<ffffffff81741957>] ? entry_SYSCALL_64_fastpath+0x12/0x6a
Code: ba ae 00 00 00 48 c7 c6 7b 71 94 81 48 c7 c7 63 71 94 81 e8 6c 0f 02 00 48 85 db 75 0e 48 c7 c7 9f 71 94 81 31 c0 e8 59 0f 02 00 <48> 83 bb a0 00 00 00 00 75 0e 48 c7 c7 ae 71 94 81 31 c0 e8 41
RIP  [<ffffffff8171a95e>] __ip6_datagram_connect+0x71e/0xa20
 RSP <ffff880129a17da8>
CR2: 00000000000000a0
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/route.c

@@ -248,12 +248,6 @@ static void ip6_rt_blackhole_redirect(struct dst_entry *dst, struct sock *sk,
 {
 }
 
-static u32 *ip6_rt_blackhole_cow_metrics(struct dst_entry *dst,
-					 unsigned long old)
-{
-	return NULL;
-}
-
 static struct dst_ops ip6_dst_blackhole_ops = {
 	.family			=	AF_INET6,
 	.destroy		=	ip6_dst_destroy,
@@ -262,7 +256,7 @@ static struct dst_ops ip6_dst_blackhole_ops = {
 	.default_advmss		=	ip6_default_advmss,
 	.update_pmtu		=	ip6_rt_blackhole_update_pmtu,
 	.redirect		=	ip6_rt_blackhole_redirect,
-	.cow_metrics		=	ip6_rt_blackhole_cow_metrics,
+	.cow_metrics		=	dst_cow_metrics_generic,
 	.neigh_lookup		=	ip6_neigh_lookup,
 };
 
@@ -319,6 +313,15 @@ static const struct rt6_info ip6_blk_hole_entry_template = {
 
 #endif
 
+static void rt6_info_init(struct rt6_info *rt)
+{
+	struct dst_entry *dst = &rt->dst;
+
+	memset(dst + 1, 0, sizeof(*rt) - sizeof(*dst));
+	INIT_LIST_HEAD(&rt->rt6i_siblings);
+	INIT_LIST_HEAD(&rt->rt6i_uncached);
+}
+
 /* allocate dst with ip6_dst_ops */
 static struct rt6_info *__ip6_dst_alloc(struct net *net,
 					struct net_device *dev,
@@ -327,13 +330,9 @@ static struct rt6_info *__ip6_dst_alloc(struct net *net,
 	struct rt6_info *rt = dst_alloc(&net->ipv6.ip6_dst_ops, dev,
 					0, DST_OBSOLETE_FORCE_CHK, flags);
 
-	if (rt) {
-		struct dst_entry *dst = &rt->dst;
+	if (rt)
+		rt6_info_init(rt);
 
-		memset(dst + 1, 0, sizeof(*rt) - sizeof(*dst));
-		INIT_LIST_HEAD(&rt->rt6i_siblings);
-		INIT_LIST_HEAD(&rt->rt6i_uncached);
-	}
 	return rt;
 }
 
@@ -1214,24 +1213,20 @@ struct dst_entry *ip6_blackhole_route(struct net *net, struct dst_entry *dst_ori
 
 	rt = dst_alloc(&ip6_dst_blackhole_ops, ort->dst.dev, 1, DST_OBSOLETE_NONE, 0);
 	if (rt) {
-		new = &rt->dst;
-
-		memset(new + 1, 0, sizeof(*rt) - sizeof(*new));
+		rt6_info_init(rt);
 
+		new = &rt->dst;
 		new->__use = 1;
 		new->input = dst_discard;
 		new->output = dst_discard_sk;
 
-		if (dst_metrics_read_only(&ort->dst))
-			new->_metrics = ort->dst._metrics;
-		else
-			dst_copy_metrics(new, &ort->dst);
+		dst_copy_metrics(new, &ort->dst);
 		rt->rt6i_idev = ort->rt6i_idev;
 		if (rt->rt6i_idev)
 			in6_dev_hold(rt->rt6i_idev);
 
 		rt->rt6i_gateway = ort->rt6i_gateway;
-		rt->rt6i_flags = ort->rt6i_flags;
+		rt->rt6i_flags = ort->rt6i_flags & ~RTF_PCPU;
 		rt->rt6i_metric = 0;
 
 		memcpy(&rt->rt6i_dst, &ort->rt6i_dst, sizeof(struct rt6key));