netdev - Re: [PATCH] Revert "ath9k: fix ath_tx_process_buffer() potential null ptr dereference"

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Date:   Thu, 18 Feb 2021 07:02:59 -0700
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Kalle Valo <kvalo@...eaurora.org>
Cc:     davem@...emloft.net, kuba@...nel.org, nbd@....name,
        ath9k-devel@....qualcomm.com, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] Revert "ath9k: fix ath_tx_process_buffer() potential null
 ptr dereference"

On 2/17/21 11:23 PM, Kalle Valo wrote:
> Shuah Khan <skhan@...uxfoundation.org> wrote:
> 
>> This reverts commit a56c14bb21b296fb6d395164ab62ef2e419e5069.
>>
>> ath_tx_process_buffer() doesn't dereference or check sta and passes it
>> to ath_tx_complete_aggr() and ath_tx_complete_buf().
>>
>> ath_tx_complete_aggr() checks the pointer before use. No problem here.
>>
>> ath_tx_complete_buf() doesn't check or dereference sta and passes it on
>> to ath_tx_complete(). ath_tx_complete() doesn't check or dereference sta,
>> but assigns it to tx_info->status.status_driver_data[0]
>>
>> ath_tx_complete_buf() is called from ath_tx_complete_aggr() passing
>> null ieee80211_sta pointer.
>>
>> There is a potential for dereference later on, if and when the
>> tx_info->status.status_driver_data[0]is referenced. In addition, the
>> rcu read lock might be released before referencing the contents.
>>
>> ath_tx_complete_buf() should be fixed to check sta perhaps? Worth
>> looking into.
>>
>> Reverting this patch because it doesn't solve the problem and introduces
>> memory leak by skipping buffer completion if the pointer (sta) is NULL.
>>
>> Fixes: a56c14bb21b2 ("ath9k: fix ath_tx_process_buffer() potential null ptr dereference")
>> Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
>> Signed-off-by: Kalle Valo <kvalo@...eaurora.org>
> 
> Thanks. I added the commit id and Fixes tag to the commit log, see the new version above.
> 

Thanks. Sorry for forgetting the Fixes tag.

thanks,
-- Shuah