linux-kernel - Re: [PATCH] drivers: net: remove a dangling pointer in peak_usb_create

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Message-ID: <CAD-N9QWvfoo_HtQ+KT-7JNFumQMaq8YqMkHGR2t7pDKsDW0hkQ@mail.gmail.com>
Date:   Fri, 21 Jan 2022 08:09:17 +0800
From:   Dongliang Mu <mudongliangabcd@...il.com>
To:     Pavel Skripkin <paskripkin@...il.com>
Cc:     Dongliang Mu <dzm91@...t.edu.cn>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Stephane Grosjean <s.grosjean@...k-system.com>,
        Stefan Mätje <stefan.maetje@....eu>,
        Vincent Mailhol <mailhol.vincent@...adoo.fr>,
        linux-can@...r.kernel.org,
        "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drivers: net: remove a dangling pointer in peak_usb_create_dev

On Thu, Jan 20, 2022 at 10:27 PM Pavel Skripkin <paskripkin@...il.com> wrote:
>
> Hi Dongliang,
>
> On 1/20/22 16:05, Dongliang Mu wrote:
> > From: Dongliang Mu <mudongliangabcd@...il.com>
> >
> > The error handling code of peak_usb_create_dev forgets to reset the
> > next_siblings of previous entry.
> >
> > Fix this by nullifying the (dev->prev_siblings)->next_siblings in the
> > error handling code.
> >
> > Signed-off-by: Dongliang Mu <mudongliangabcd@...il.com>
> > ---
> >   drivers/net/can/usb/peak_usb/pcan_usb_core.c | 3 +++
> >   1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/net/can/usb/peak_usb/pcan_usb_core.c b/drivers/net/can/usb/peak_usb/pcan_usb_core.c
> > index b850ff8fe4bd..f858810221b6 100644
> > --- a/drivers/net/can/usb/peak_usb/pcan_usb_core.c
> > +++ b/drivers/net/can/usb/peak_usb/pcan_usb_core.c
> > @@ -894,6 +894,9 @@ static int peak_usb_create_dev(const struct peak_usb_adapter *peak_usb_adapter,
> >               dev->adapter->dev_free(dev);
> >
> >   lbl_unregister_candev:
> > +     /* remove the dangling pointer in next_siblings */
> > +     if (dev->prev_siblings)
> > +             (dev->prev_siblings)->next_siblings = NULL;
> >       unregister_candev(netdev);
> >
> >   lbl_restore_intf_data:
>
>
> Is this pointer used somewhere? I see, that couple of
> struct peak_usb_adapter::dev_free() functions use it, but
> peak_usb_disconnect() sets dev->next_siblings to NULL before calling
> ->dev_free().
>
> Do you have a calltrace or oops log?

Hi Pavel,

I have no calltrace or log since this dangling pointer may not be
dereferenced in the following code. But I am not sure. So the commit
title of this patch is "remove a dangling pointer in
peak_usb_create_dev".

>
>
>
>
> With regards,
> Pavel Skripkin