Re: [PATCH v2] mwl8k: fix possible race condition in info->control.sta use

[Christian Lamparter <chunkeey@xxxxxxxxxxxxxx>]

On Wed, Jul 11, 2012 at 7:32 AM, Thomas Huehn
<thomas@xxxxxxxxxxxxxxxxxxxxxxx> wrote:
> info->control.sta may only be dereferenced during the drv_tx call otherwise
> could lead to use-after-free bugs

Don"t forget many ieee80211_sta_* functions have to be called under RCU
lock and the resulting pointer is only valid under RCU lock as well.

>
> diff --git a/drivers/net/wireless/mwl8k.c b/drivers/net/wireless/mwl8k.c
> index df6c6f1..eec5cd1 100644
> --- a/drivers/net/wireless/mwl8k.c
> +++ b/drivers/net/wireless/mwl8k.c
> @@ -1667,7 +1667,8 @@ mwl8k_txq_reclaim(struct ieee80211_hw *hw,
>
>                 info = IEEE80211_SKB_CB(skb);
>                 if (ieee80211_is_data(wh->frame_control)) {

+                         rcu_read_lock();

> -                       sta = info->control.sta;
> +                       sta = ieee80211_find_sta_by_ifaddr(hw, wh->addr1,
> +                                                          wh->addr2);
>                         if (sta) {
>                                 sta_info = MWL8K_STA(sta);
>                                 BUG_ON(sta_info == NULL);
>                                 [...]
>                         }

+                         rcu_read_unlock();

Regards,
      Chr
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