Thread (4 messages) flat view 4 messages, 3 authors, 2022-06-15

Re: [syzbot] WARNING: ODEBUG bug in route4_destroy

From: Dan Carpenter <hidden>
Date: 2022-06-14 14:47:20
Also in: lkml

On Tue, Jun 14, 2022 at 10:35:44PM +0800, 'Zhen Chen' via syzkaller-bugs wrote:
quoted hunk ↗ jump to hunk
This looks like  route4_destroy is deleting the 'fold' which has been
freed by tcf_queue_work in route4_change. It means 'fold' is still in
the table.
I have tested this patch on syzbot and it works well, but I am not
sure whether it will introduce other issues...
diff --git a/net/sched/cls_route.c b/net/sched/cls_route.c
index a35ab8c27866..758c21f9d628 100644
--- a/net/sched/cls_route.c
+++ b/net/sched/cls_route.c
@@ -526,7 +526,7 @@ 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 && f->handle != fold->handle) {
                                 ^^^^^^^^^^^^
There is still a dereference here so your patch doesn't make sense. :/

regards,
dan carpenter
 		th = to_hash(fold->handle);
 		h = from_hash(fold->handle >> 16);
 		b = rtnl_dereference(head->table[th]);

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