userns xt_recent: Specify the owner/group of ip_list_perms in the initial user namespace

xt_recent creates a bunch of proc files and initializes their uid
and gids to the values of ip_list_uid and ip_list_gid. When
initialize those proc files convert those values to kuids so they
can continue to reside on the /proc inode.

Cc: Pablo Neira Ayuso <[e-mail]>
Cc: Patrick McHardy <[e-mail]>
Cc: Jan Engelhardt <[e-mail]>
Acked-by: David S. Miller <[e-mail]>
Acked-by: Serge Hallyn <[e-mail]>
Signed-off-by: Eric W. Biederman <[e-mail]>

init/Kconfig

···
 	# Networking
 	depends on NET_9P = n
 	depends on NETFILTER_XT_MATCH_OWNER = n
-	depends on NETFILTER_XT_MATCH_RECENT = n
 	depends on AF_RXRPC = n
 	depends on NET_KEY = n
 	depends on DNS_RESOLVER = n

net/netfilter/xt_recent.c

···
 	struct recent_table *t;
 #ifdef CONFIG_PROC_FS
 	struct proc_dir_entry *pde;
+	kuid_t uid;
+	kgid_t gid;
 #endif
 	unsigned int i;
 	int ret = -EINVAL;
···
 	for (i = 0; i < ip_list_hash_size; i++)
 		INIT_LIST_HEAD(&t->iphash[i]);
 #ifdef CONFIG_PROC_FS
+	uid = make_kuid(&init_user_ns, ip_list_uid);
+	gid = make_kgid(&init_user_ns, ip_list_gid);
+	if (!uid_valid(uid) || !gid_valid(gid)) {
+		kfree(t);
+		ret = -EINVAL;
+		goto out;
+	}
 	pde = proc_create_data(t->name, ip_list_perms, recent_net->xt_recent,
 		  &recent_mt_fops, t);
 	if (pde == NULL) {
···
 		ret = -ENOMEM;
 		goto out;
 	}
-	pde->uid = ip_list_uid;
-	pde->gid = ip_list_gid;
+	pde->uid = uid;
+	pde->gid = gid;
 #endif
 	spin_lock_bh(&recent_lock);
 	list_add_tail(&t->list, &recent_net->tables);