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

[Thomas Huehn <thomas@xxxxxxxxxxxxxxxxxxxxxxx>]

Hi Christian,

You have a very valid point here.
I will send a v3.

Greetings Thomas

Christian Lamparter schrieb:

> 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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