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

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Date:   Mon, 06 Nov 2023 16:41:45 +0200
From:   Kalle Valo <kvalo@...nel.org>
To:     Zheng Wang <zyytlz.wz@....com>
Cc:     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, arend.vanspriel@...adcom.com,
        SHA-cyfmac-dev-list@...ineon.com, linux-kernel@...r.kernel.org,
        security@...nel.org, stable@...r.kernel.org,
        hackerzheng666@...il.com
Subject: Re: [PATCH v5] wifi: brcmfmac: Fix use-after-free bug in
  brcmf_cfg80211_detach

Zheng Wang <zyytlz.wz@....com> 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@....com>
> Cc: stable@...r.kernel.org
> ---
> 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@163.com/

-- 
https://patchwork.kernel.org/project/linux-wireless/list/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches