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

[Zheng Hacker]

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.
As I'm not very familiar with the logic here. I'm still not sure if we
should delete the timer_shutdown_sync.
Looking forward to your reply :)

```cpp
if (cfg->int_escan_map || cfg->scan_request) {
    escan->escan_state = WL_ESCAN_STATE_IDLE;
    brcmf_notify_escan_complete(cfg, escan->ifp, true, true);
  }
```

Best regards,
Zheng

>
> Regards,
> Arend
>
> >
> > Kalle Valo <kvalo@xxxxxxxxxx> 于2023年11月6日周一 22:41写道：
> >>
> >> Zheng Wang <zyytlz.wz@xxxxxxx> writes:
> >>
> >>> This is the candidate patch of CVE-2023-47233 :
> >>> https://nvd.nist.gov/vuln/detail/CVE-2023-47233
> >>>
> >>> In brcm80211 driver,it starts with the following invoking chain
> >>> to start init a timeout worker:
> >>>
> >>> ->brcmf_usb_probe
> >>> ->brcmf_usb_probe_cb
> >>> ->brcmf_attach
> >>> ->brcmf_bus_started
> >>>  ->brcmf_cfg80211_attach
> >>>    ->wl_init_priv
> >>>      ->brcmf_init_escan
> >>>        ->INIT_WORK(&cfg->escan_timeout_work,
> >>>          brcmf_cfg80211_escan_timeout_worker);
> >>>
> >>> If we disconnect the USB by hotplug, it will call
> >>> brcmf_usb_disconnect to make cleanup. The invoking chain is :
> >>>
> >>> brcmf_usb_disconnect
> >>> ->brcmf_usb_disconnect_cb
> >>> ->brcmf_detach
> >>> ->brcmf_cfg80211_detach
> >>>  ->kfree(cfg);
> >>>
> >>> While the timeout woker may still be running. This will cause
> >>> a use-after-free bug on cfg in brcmf_cfg80211_escan_timeout_worker.
> >>>
> >>> Fix it by deleting the timer and canceling the worker in
> >>> brcmf_cfg80211_detach.
> >>>
> >>> Fixes: e756af5b30b0 ("brcmfmac: add e-scan support.")
> >>> Signed-off-by: Zheng Wang <zyytlz.wz@xxxxxxx>
> >>> Cc: stable@xxxxxxxxxxxxxxx
> >>> ---
> >>> v5:
> >>> - replace del_timer_sync with timer_shutdown_sync suggested by
> >>> Arend and Takashi
> >>> v4:
> >>> - rename the subject and add CVE number as Ping-Ke Shih suggested
> >>> v3:
> >>> - rename the subject as Johannes suggested
> >>> v2:
> >>> - fix the error of kernel test bot reported
> >>> ---
> >>> drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c | 2 ++
> >>> 1 file changed, 2 insertions(+)
> >>>
> >>> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> >>> b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> >>> index 667462369a32..a8723a61c9e4 100644
> >>> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> >>> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> >>> @@ -8431,6 +8431,8 @@ void brcmf_cfg80211_detach(struct brcmf_cfg80211_info
> >>> *cfg)
> >>> if (!cfg)
> >>>        return;
> >>>
> >>> +     timer_shutdown_sync(&cfg->escan_timeout);
> >>> +     cancel_work_sync(&cfg->escan_timeout_work);
> >>> brcmf_pno_detach(cfg);
> >>> brcmf_btcoex_detach(cfg);
> >>> wiphy_unregister(cfg->wiphy);
> >>
> >> Has anyone tested this on a real device? As v1 didn't even compile I am
> >> very cautious:
> >>
> >> https://patchwork.kernel.org/project/linux-wireless/patch/20231104054709.716585-1-zyytlz.wz@xxxxxxx/
> >>
> >> --
> >> https://patchwork.kernel.org/project/linux-wireless/list/
> >>
> >> https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
>
>
>