xfrm: route MIGRATE notifications to caller's netns

xfrm_send_migrate() in net/xfrm/xfrm_user.c and pfkey_send_migrate()
in net/key/af_key.c both hardcode &init_net for the multicast that
announces a successful XFRM_MSG_MIGRATE / SADB_X_MIGRATE.

XFRM_MSG_MIGRATE arrives on a per-netns NETLINK_XFRM socket, and the
rest of the xfrm/af_key netlink path was made netns-aware in 2008.
The other 14 multicast paths in xfrm_user.c route their event using
xs_net(x), xp_net(xp) or sock_net(skb->sk); only the migrate path
was missed.

Two consequences of the init_net hardcoding:

  1. The notification (selector, old/new endpoint addresses, and the
     km_address) is delivered to listeners on init_net's
     XFRMNLGRP_MIGRATE / pfkey BROADCAST_ALL groups rather than on
     the issuing netns. An IKE daemon running in init_net therefore
     receives migration notifications originating from any other
     netns on the host.

  2. An IKE daemon running inside a non-init netns and subscribed
     to its own XFRMNLGRP_MIGRATE / pfkey groups never receives the
     notification of its own migration. IKEv2 MOBIKE / address-update
     handling inside a netns is silently broken.

Thread struct net through km_migrate() and the xfrm_mgr.migrate
function pointer, drop the &init_net override in xfrm_send_migrate()
and pfkey_send_migrate(), and pass the caller's net (already in
scope in xfrm_migrate() via sock_net(skb->sk)) all the way down.
struct xfrm_mgr is in-tree only and not exported as a stable API,
so the function-pointer signature change is internal.

pfkey_broadcast() is already netns-aware via net_generic(net,
pfkey_net_id) since the pernet conversion. The five other
pfkey_broadcast() callers in af_key.c already pass xs_net(x),
sock_net(sk) or a per-netns net, so this only removes the
&init_net outlier.

Fixes: 5c79de6e79 ("[XFRM]: User interface for handling XFRM_MSG_MIGRATE")
Cc: stable@vger.kernel.org # v5.15+
Signed-off-by: Maoyi Xie <maoyi.xie@ntu.edu.sg>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

include/net/xfrm.h

@@ -715,6 +715,7 @@ struct xfrm_mgr {
 					   const struct xfrm_migrate *m,
 					   int num_bundles,
 					   const struct xfrm_kmaddress *k,
+					   struct net *net,
 					   const struct xfrm_encap_tmpl *encap);
 	bool			(*is_alive)(const struct km_event *c);
 };
@@ -1891,7 +1892,7 @@ int xfrm_sk_policy_insert(struct sock *sk, int dir, struct xfrm_policy *pol);
 #ifdef CONFIG_XFRM_MIGRATE
 int km_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 	       const struct xfrm_migrate *m, int num_bundles,
-	       const struct xfrm_kmaddress *k,
+	       const struct xfrm_kmaddress *k, struct net *net,
 	       const struct xfrm_encap_tmpl *encap);
 struct xfrm_state *xfrm_migrate_state_find(struct xfrm_migrate *m, struct net *net,
 						u32 if_id);

net/key/af_key.c

@@ -3564,7 +3564,7 @@ static int set_ipsecrequest(struct sk_buff *skb,
 #ifdef CONFIG_NET_KEY_MIGRATE
 static int pfkey_send_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 			      const struct xfrm_migrate *m, int num_bundles,
-			      const struct xfrm_kmaddress *k,
+			      const struct xfrm_kmaddress *k, struct net *net,
 			      const struct xfrm_encap_tmpl *encap)
 {
 	int i;
@@ -3669,7 +3669,7 @@ static int pfkey_send_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 	}
 
 	/* broadcast migrate message to sockets */
-	pfkey_broadcast(skb, GFP_ATOMIC, BROADCAST_ALL, NULL, &init_net);
+	pfkey_broadcast(skb, GFP_ATOMIC, BROADCAST_ALL, NULL, net);
 
 	return 0;
 
@@ -3680,7 +3680,7 @@ err:
 #else
 static int pfkey_send_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 			      const struct xfrm_migrate *m, int num_bundles,
-			      const struct xfrm_kmaddress *k,
+			      const struct xfrm_kmaddress *k, struct net *net,
 			      const struct xfrm_encap_tmpl *encap)
 {
 	return -ENOPROTOOPT;

net/xfrm/xfrm_policy.c

@@ -4703,7 +4703,7 @@ int xfrm_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 	}
 
 	/* Stage 5 - announce */
-	km_migrate(sel, dir, type, m, num_migrate, k, encap);
+	km_migrate(sel, dir, type, m, num_migrate, k, net, encap);
 
 	xfrm_pol_put(pol);
 

net/xfrm/xfrm_state.c

@@ -2837,7 +2837,7 @@ EXPORT_SYMBOL(km_policy_expired);
 #ifdef CONFIG_XFRM_MIGRATE
 int km_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 	       const struct xfrm_migrate *m, int num_migrate,
-	       const struct xfrm_kmaddress *k,
+	       const struct xfrm_kmaddress *k, struct net *net,
 	       const struct xfrm_encap_tmpl *encap)
 {
 	int err = -EINVAL;
@@ -2848,7 +2848,7 @@ int km_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 	list_for_each_entry_rcu(km, &xfrm_km_list, list) {
 		if (km->migrate) {
 			ret = km->migrate(sel, dir, type, m, num_migrate, k,
-					  encap);
+					  net, encap);
 			if (!ret)
 				err = ret;
 		}

net/xfrm/xfrm_user.c

@@ -3271,10 +3271,9 @@ out_cancel:
 
 static int xfrm_send_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 			     const struct xfrm_migrate *m, int num_migrate,
-			     const struct xfrm_kmaddress *k,
+			     const struct xfrm_kmaddress *k, struct net *net,
 			     const struct xfrm_encap_tmpl *encap)
 {
-	struct net *net = &init_net;
 	struct sk_buff *skb;
 	int err;
 
@@ -3292,7 +3291,7 @@ static int xfrm_send_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 #else
 static int xfrm_send_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 			     const struct xfrm_migrate *m, int num_migrate,
-			     const struct xfrm_kmaddress *k,
+			     const struct xfrm_kmaddress *k, struct net *net,
 			     const struct xfrm_encap_tmpl *encap)
 {
 	return -ENOPROTOOPT;