net: ipmr: fix static mfc/dev leaks on table destruction

When destroying an mrt table the static mfc entries and the static
devices are kept, which leads to devices that can never be destroyed
(because of refcnt taken) and leaked memory, for example:
unreferenced object 0xffff880034c144c0 (size 192):
comm "mfc-broken", pid 4777, jiffies 4320349055 (age 46001.964s)
hex dump (first 32 bytes):
98 53 f0 34 00 88 ff ff 98 53 f0 34 00 88 ff ff .S.4.....S.4....
ef 0a 0a 14 01 02 03 04 00 00 00 00 01 00 00 00 ................
backtrace:
[<ffffffff815c1b9e>] kmemleak_alloc+0x4e/0xb0
[<ffffffff811ea6e0>] kmem_cache_alloc+0x190/0x300
[<ffffffff815931cb>] ip_mroute_setsockopt+0x5cb/0x910
[<ffffffff8153d575>] do_ip_setsockopt.isra.11+0x105/0xff0
[<ffffffff8153e490>] ip_setsockopt+0x30/0xa0
[<ffffffff81564e13>] raw_setsockopt+0x33/0x90
[<ffffffff814d1e14>] sock_common_setsockopt+0x14/0x20
[<ffffffff814d0b51>] SyS_setsockopt+0x71/0xc0
[<ffffffff815cdbf6>] entry_SYSCALL_64_fastpath+0x16/0x7a
[<ffffffffffffffff>] 0xffffffffffffffff

Make sure that everything is cleaned on netns destruction.

Signed-off-by: Nikolay Aleksandrov <[e-mail]>
Reviewed-by: Cong Wang <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv4/ipmr.c

···
 			      struct mfc_cache *c, struct rtmsg *rtm);
 static void mroute_netlink_event(struct mr_table *mrt, struct mfc_cache *mfc,
 				 int cmd);
-static void mroute_clean_tables(struct mr_table *mrt);
+static void mroute_clean_tables(struct mr_table *mrt, bool all);
 static void ipmr_expire_process(unsigned long arg);
 
 #ifdef CONFIG_IP_MROUTE_MULTIPLE_TABLES
···
 static void ipmr_free_table(struct mr_table *mrt)
 {
 	del_timer_sync(&mrt->ipmr_expire_timer);
-	mroute_clean_tables(mrt);
+	mroute_clean_tables(mrt, true);
 	kfree(mrt);
 }
 
···
  *	Close the multicast socket, and clear the vif tables etc
  */
 
-static void mroute_clean_tables(struct mr_table *mrt)
+static void mroute_clean_tables(struct mr_table *mrt, bool all)
 {
 	int i;
 	LIST_HEAD(list);
···
 	/* Shut down all active vif entries */
 
 	for (i = 0; i < mrt->maxvif; i++) {
-		if (!(mrt->vif_table[i].flags & VIFF_STATIC))
-			vif_delete(mrt, i, 0, &list);
+		if (!all && (mrt->vif_table[i].flags & VIFF_STATIC))
+			continue;
+		vif_delete(mrt, i, 0, &list);
 	}
 	unregister_netdevice_many(&list);
 
···
 
 	for (i = 0; i < MFC_LINES; i++) {
 		list_for_each_entry_safe(c, next, &mrt->mfc_cache_array[i], list) {
-			if (c->mfc_flags & MFC_STATIC)
+			if (!all && (c->mfc_flags & MFC_STATIC))
 				continue;
 			list_del_rcu(&c->list);
 			mroute_netlink_event(mrt, c, RTM_DELROUTE);
···
 						    NETCONFA_IFINDEX_ALL,
 						    net->ipv4.devconf_all);
 			RCU_INIT_POINTER(mrt->mroute_sk, NULL);
-			mroute_clean_tables(mrt);
+			mroute_clean_tables(mrt, false);
 		}
 	}
 	rtnl_unlock();