UBUNTU: SAUCE: net_sched: cls_route: remove from list when handle is 0

When a route filter is replaced and the old filter has a 0 handle, the old
one won't be removed from the hashtable, while it will still be freed.

The test was there since before commit 1109c00 ("net: sched: RCU
cls_route"), when a new filter was not allocated when there was an old one.
The old filter was reused and the reinserting would only be necessary if an
old filter was replaced. That was still wrong for the same case where the
old handle was 0.

Remove the old filter from the list independently from its handle value.

This fixes CVE-2022-2588, also reported as ZDI-CAN-17440.

Bug 3768351

Reported-by: Zhenpeng Lin <[email protected]>
Signed-off-by: Thadeu Lima de Souza Cascardo <[email protected]>
Reviewed-by: Kamal Mostafa <[email protected]>
CVE-2022-2588
Acked-by: Kamal Mostafa <[email protected]>
Acked-by: Luke Nowakowski-Krijger <[email protected]>

Change-Id: Id3c4d77901901fc489a6cd47bb22442676b6ed2b
Reviewed-on: https://git-master.nvidia.com/r/c/linux-4.9/+/2766342
Reviewed-by: Bibek Basu <[email protected]>
GVS: Gerrit_Virtual_Submit <[email protected]>
Tested-by: Amulya Yarlagadda <[email protected]>

net/sched/cls_route.c

@@ -534,7 +534,7 @@ static int route4_change(struct net *net, struct sk_buff *in_skb,
 	rcu_assign_pointer(f->next, f1);
 	rcu_assign_pointer(*fp, f);
 
-	if (fold && fold->handle && f->handle != fold->handle) {
+	if (fold) {
 		th = to_hash(fold->handle);
 		h = from_hash(fold->handle >> 16);
 		b = rtnl_dereference(head->table[th]);