netdev - Re: [PATCH net v4 12/12] virt_wifi: fix refcnt leak in module exit routine

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Date:   Tue, 8 Oct 2019 15:53:48 +0900
From:   Taehee Yoo <ap420073@...il.com>
To:     Sabrina Dubroca <sd@...asysnail.net>
Cc:     David Miller <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>, linux-wireless@...r.kernel.org,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Johannes Berg <johannes@...solutions.net>,
        j.vosburgh@...il.com, vfalico@...il.com,
        Andy Gospodarek <andy@...yhouse.net>,
        Jiří Pírko <jiri@...nulli.us>,
        Roopa Prabhu <roopa@...ulusnetworks.com>, saeedm@...lanox.com,
        manishc@...vell.com, rahulv@...vell.com, kys@...rosoft.com,
        haiyangz@...rosoft.com,
        Stephen Hemminger <stephen@...workplumber.org>,
        sashal@...nel.org, hare@...e.de, varun@...lsio.com,
        ubraun@...ux.ibm.com, kgraul@...ux.ibm.com,
        Jay Vosburgh <jay.vosburgh@...onical.com>,
        Cody Schuffelen <schuffelen@...gle.com>, bjorn@...k.no
Subject: Re: [PATCH net v4 12/12] virt_wifi: fix refcnt leak in module exit routine

On Mon, 7 Oct 2019 at 20:22, Sabrina Dubroca <sd@...asysnail.net> wrote:
>

Hi Sabrina,
Thank you for the review!

> 2019-09-28, 16:48:43 +0000, Taehee Yoo wrote:
> > virt_wifi_newlink() calls netdev_upper_dev_link() and it internally
> > holds reference count of lower interface.
> >
> > Current code does not release a reference count of the lower interface
> > when the lower interface is being deleted.
> > So, reference count leaks occur.
> >
> > Test commands:
> >     ip link add dummy0 type dummy
> >     ip link add vw1 link dummy0 type virt_wifi
>
> There should also be "ip link del dummy0" in this reproducer, right?
>
> [...]
>
> > @@ -598,14 +634,24 @@ static int __init virt_wifi_init_module(void)
> >       /* Guaranteed to be locallly-administered and not multicast. */
> >       eth_random_addr(fake_router_bssid);
> >
> > +     err = register_netdevice_notifier(&virt_wifi_notifier);
> > +     if (err)
> > +             return err;
> > +
>
> Here err is 0.
>
> >       common_wiphy = virt_wifi_make_wiphy();
> >       if (!common_wiphy)
> > -             return -ENOMEM;
> > +             goto notifier;
>
> err is still 0 when we jump...
>
> >       err = rtnl_link_register(&virt_wifi_link_ops);
> >       if (err)
> > -             virt_wifi_destroy_wiphy(common_wiphy);
> > +             goto destroy_wiphy;
> >
> > +     return 0;
> > +
> > +destroy_wiphy:
> > +     virt_wifi_destroy_wiphy(common_wiphy);
> > +notifier:
> > +     unregister_netdevice_notifier(&virt_wifi_notifier);
> >       return err;
> >  }
>
> ... so now we return 0 on failure. Can you add an "err = -ENOMEM"
> before "common_wiphy = ..."?
>

You're right, I will fix this in a v5 patch!

Thanks!

> Thanks.
>
> --
> Sabrina