Re: [PATCH v5] wifi: brcmfmac: Fix use-after-free bug in brcmf_cfg80211_detach

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On November 17, 2023 3:31:40 AM Zheng Hacker <hackerzheng666@xxxxxxxxx> wrote:

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.

No top posting please!

The timer context is softirq and worker is thread context. The ability to sleep is the big difference between the two or at least the reason for using them here.

Regards,
Arend


Takashi Iwai <tiwai@xxxxxxx> 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@xxxxxxxxx> wrote:

Arend van Spriel <arend.vanspriel@xxxxxxxxxxxx> 于2023年11月13日周一 17:18写道:

On November 8, 2023 4:03:26 AM Zheng Hacker <hackerzheng666@xxxxxxxxx>
wrote:

Arend Van Spriel <arend.vanspriel@xxxxxxxxxxxx> 于2023年11月6日周一 23:48写道:

On November 6, 2023 3:44:53 PM Zheng Hacker <hackerzheng666@xxxxxxxxx> 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



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