netdev - Re: [PATCH net-next 1/2] net/sched: act

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CANn89i+zDW5ttPZ7fw2gDbVQqXj2uFoeEeTRSU6gzFLM3zGCeA@mail.gmail.com>
Date: Wed, 26 Nov 2025 12:29:58 -0800
From: Eric Dumazet <edumazet@...gle.com>
To: Jamal Hadi Salim <jhs@...atatu.com>
Cc: Jakub Kicinski <kuba@...nel.org>, davem@...emloft.net, pabeni@...hat.com, 
	jiri@...nulli.us, xiyou.wangcong@...il.com, netdev@...r.kernel.org, 
	dcaratti@...hat.com
Subject: Re: [PATCH net-next 1/2] net/sched: act_mirred: Fix infinite loop

On Wed, Nov 26, 2025 at 12:20 PM Jamal Hadi Salim <jhs@...atatu.com> wrote:
>
> On Wed, Nov 26, 2025 at 1:20 PM Eric Dumazet <edumazet@...gle.com> wrote:
> >
> > On Wed, Nov 26, 2025 at 10:14 AM Jamal Hadi Salim <jhs@...atatu.com> wrote:
> >
> > > It's the multiport redirection, particularly to ingress. When it get
> > > redirected to ingress it will get queued and then transitioned back.
> > > xmit struct wont catch this as a recursion, so MIRRED_NEST_LIMIT will
> > > not help you.
> > > Example (see the first accompanying tdc test):
> > > packet showing up on port0:ingress mirred redirect --> port1:egress
> > > packet showing up on port1:egress mirred redirect --> port0:ingress
> >
> > Have you tried recording both devices ?
> >
> > diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
> > index f27b583def78e4afecc7112854b93d59c2520201..711fc2e31cb0451c07a39f9c94226357d5faec09
> > 100644
> > --- a/net/sched/act_mirred.c
> > +++ b/net/sched/act_mirred.c
> > @@ -445,15 +445,17 @@ TC_INDIRECT_SCOPE int tcf_mirred_act(struct sk_buff *skb,
> >                 return retval;
> >         }
> >         for (i = 0; i < xmit->sched_mirred_nest; i++) {
> > -               if (xmit->sched_mirred_dev[i] != dev)
> > +               if (xmit->sched_mirred_dev[i] != dev &&
> > +                   xmit->sched_mirred_dev[i] != skb->dev)
> >                         continue;
> > -               pr_notice_once("tc mirred: loop on device %s\n",
> > -                              netdev_name(dev));
> > +               pr_notice_once("tc mirred: loop on device %s/%s\n",
> > +                              netdev_name(dev), netdev_name(skb->dev));
> >                 tcf_action_inc_overlimit_qstats(&m->common);
> >                 return retval;
> >         }
> >
> >         xmit->sched_mirred_dev[xmit->sched_mirred_nest++] = dev;
> > +       xmit->sched_mirred_dev[xmit->sched_mirred_nest++] = skb->dev;
> >
> >         m_mac_header_xmit = READ_ONCE(m->tcfm_mac_header_xmit);
> >         m_eaction = READ_ONCE(m->tcfm_eaction);
>
> Did you mean not to decrement sched_mirred_nest twice?

No, sorry, we should decrement twice of course.

> I dont have time today but will continue early AM.
>
> cheers,
> jamal