netdev - Re: [PATCH] 4.9.13 brcmfmac: fix use-after-free on resume

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Date:   Mon, 6 Mar 2017 14:00:09 +0100
From:   Arend Van Spriel <arend.vanspriel@...adcom.com>
To:     Daniel J Blueman <daniel@...ra.org>,
        Hante Meuleman <hante.meuleman@...adcom.com>,
        Pieter-Paul Giesberts <pieterpg@...adcom.com>
Cc:     Netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        linux-wireless <linux-wireless@...r.kernel.org>
Subject: Re: [PATCH] 4.9.13 brcmfmac: fix use-after-free on resume

+ linux-wireless

On 6-3-2017 8:14, Daniel J Blueman wrote:
> KASAN reported 'struct wireless_dev wdev' was read after being freed.
> Fix by freeing after the access.

I would rather like to see the KASAN report, because something is off
here. This function is called with wdev as a parameter so how can it be
accessed after free here? brcmf_remove_interface() does not free the
wdev nor the brcmf_cfg80211_vif instance which contains the wdev.

Regards,
Arend

> Signed-off-by: Daniel J Blueman <daniel@...ra.org>
> 
> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
> b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
> index de19c7c..aa0f470 100644
> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
> @@ -2288,12 +2288,13 @@ int brcmf_p2p_del_vif(struct wiphy *wiphy,
> struct wireless_dev *wdev)
>                 else
>                         err = 0;
>         }
> -       brcmf_remove_interface(vif->ifp, true);
> 
> -       brcmf_cfg80211_arm_vif_event(cfg, NULL);
>         if (vif->wdev.iftype != NL80211_IFTYPE_P2P_DEVICE)
>                 p2p->bss_idx[P2PAPI_BSSCFG_CONNECTION].vif = NULL;
> 
> +       brcmf_remove_interface(vif->ifp, true);
> +       brcmf_cfg80211_arm_vif_event(cfg, NULL);
> +
>         return err;
>  }
>