[PATCH] wifi: mac80211: change initialize for sk_buff in ieee80211_tx_dequeue()

[Alexander Wetzel]

On 05.01.23 06:26, Guenter Roeck wrote:
> On Mon, Dec 12, 2022 at 03:36:07AM -0500, Wen Gong wrote:
>> The sk_buff is only set to NULL when initialize, sometimes it will goto
>> label "begin" after ieee80211_free_txskb(), then it points to a sk_buff
>> which is already freed. If it run into the "goto out" after arrived to
>> label "begin", then it will return a sk_buff which is freed, it is a
>> risk for use-after-free.
>>
>> Fixes: ded4698b58cb ("mac80211: run late dequeue late tx handlers without holding fq->lock")
>> Signed-off-by: Wen Gong <quic_wgong at quicinc.com>
> 
> I don't see any progress on this patch. Is there a problem with it ?
> Did it get lost ?
> 

Looks ok for me. But I just noticed that my patch
https://patchwork.kernel.org/project/linux-wireless/patch/20221230121850.218810-1-alexander@wetzel-home.de/

should also fix the issue as an unintended side effect.

Alexander

> Thanks,
> Guenter
> 
>> ---
>>   net/mac80211/tx.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>>
>> base-commit: 922932ca02191a390f7f52fb6e21c44b50e14025
>>
>> diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
>> index 2171cd1ca807..0b23cc9ab9c7 100644
>> --- a/net/mac80211/tx.c
>> +++ b/net/mac80211/tx.c
>> @@ -3776,7 +3776,7 @@ struct sk_buff *ieee80211_tx_dequeue(struct ieee80211_hw *hw,
>>   	struct ieee80211_local *local = hw_to_local(hw);
>>   	struct txq_info *txqi = container_of(txq, struct txq_info, txq);
>>   	struct ieee80211_hdr *hdr;
>> -	struct sk_buff *skb = NULL;
>> +	struct sk_buff *skb;
>>   	struct fq *fq = &local->fq;
>>   	struct fq_tin *tin = &txqi->tin;
>>   	struct ieee80211_tx_info *info;
>> @@ -3790,6 +3790,8 @@ struct sk_buff *ieee80211_tx_dequeue(struct ieee80211_hw *hw,
>>   		return NULL;
>>   
>>   begin:
>> +	skb = NULL;
>> +
>>   	spin_lock_bh(&fq->lock);
>>   
>>   	if (test_bit(IEEE80211_TXQ_STOP, &txqi->flags) ||