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SubjectRe: [syzbot] WARNING: ODEBUG bug in route4_destroy
On Tue, Jun 14, 2022 at 10:35:44PM +0800, 'Zhen Chen' via syzkaller-bugs wrote:
>
> 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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