linux-kernel - Re: [PATCH v5] wifi: brcmfmac: Fix use-after-free bug in brcmf_cfg80211

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Date:   Fri, 17 Nov 2023 10:31:26 +0800
From:   Zheng Hacker <hackerzheng666@...il.com>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     Arend Van Spriel <arend.vanspriel@...adcom.com>,
        Kalle Valo <kvalo@...nel.org>, Zheng Wang <zyytlz.wz@....com>,
        aspriel@...il.com, franky.lin@...adcom.com,
        hante.meuleman@...adcom.com, johannes.berg@...el.com,
        marcan@...can.st, linus.walleij@...aro.org,
        jisoo.jang@...sei.ac.kr, linuxlovemin@...sei.ac.kr,
        wataru.gohda@...ress.com, linux-wireless@...r.kernel.org,
        brcm80211-dev-list.pdl@...adcom.com,
        SHA-cyfmac-dev-list@...ineon.com, linux-kernel@...r.kernel.org,
        security@...nel.org, stable@...r.kernel.org
Subject: Re: [PATCH v5] wifi: brcmfmac: Fix use-after-free bug in brcmf_cfg80211_detach

Yes, that makes this issue hard to fix. I was wondering why it binds the
worker with the timer rather than using just one of them.

Takashi Iwai <tiwai@...e.de> 于2023年11月17日周五 02:25写道：
>
> On Thu, 16 Nov 2023 19:20:06 +0100,
> Arend Van Spriel wrote:
> >
> > On November 15, 2023 4:00:46 PM Zheng Hacker <hackerzheng666@...il.com> wrote:
> >
> > > Arend van Spriel <arend.vanspriel@...adcom.com> 于2023年11月13日周一 17:18写道：
> > >>
> > >> On November 8, 2023 4:03:26 AM Zheng Hacker <hackerzheng666@...il.com>
> > >> wrote:
> > >>
> > >>> Arend Van Spriel <arend.vanspriel@...adcom.com> 于2023年11月6日周一 23:48写道：
> > >>>>
> > >>>> On November 6, 2023 3:44:53 PM Zheng Hacker <hackerzheng666@...il.com> wrote:
> > >>>>
> > >>>>> Thanks! I didn't test it for I don't have a device. Very appreciated
> > >>>>> if anyone could help with that.
> > >>>>
> > >>>> I would volunteer, but it made me dig deep and not sure if there is a
> > >>>> problem to solve here.
> > >>>>
> > >>>> brcmf_cfg80211_detach() calls wl_deinit_priv() -> brcmf_abort_scanning() ->
> > >>>> brcmf_notify_escan_complete() which does delete the timer.
> > >>>>
> > >>>> What am I missing here?
> > >>>
> > >>> Thanks four your detailed review. I did see the code and not sure if
> > >>> brcmf_notify_escan_complete
> > >>> would be triggered for sure. So in the first version I want to delete
> > >>> the pending timer ahead of time.
> > >>
> > >> Why requesting a CVE when you are not sure? Seems a bit hasty to put it
> > >> mildly.
> > >
> > > I'm sure the issue exists because there's only cancler of timer but not woker.
> > > As there's similar CVEs before like : https://github.com/V4bel/CVE-2022-41218,
> > > I submit it as soon as I found it.
> >
> > Ah, yes. The cancel_work_sync() can also be done in
> > brcmf_notify_escan_complete().
>
> AFAIUC, brcmf_notify_scan_complete() is called from the work itself,
> too, hence you can't issue cancel_work_sync() there (unless you make
> it conditional).
>
>
> Takashi