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Subject: Re: [PATCH 2/2] ath9k: fix ath_tx_process_buffer() potential null ptr
 dereference
To:     Kalle Valo <kvalo@codeaurora.org>
Cc:     Felix Fietkau <nbd@nbd.name>, davem@davemloft.net, kuba@kernel.org,
        ath9k-devel@qca.qualcomm.com, linux-wireless@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        Shuah Khan <skhan@linuxfoundation.org>
References: <43ed9abb9e8d7112f3cc168c2f8c489e253635ba.1613090339.git.skhan@linuxfoundation.org>
 <20210216070336.D138BC43463@smtp.codeaurora.org>
 <0fd9a538-e269-e10e-a7f9-02d4c5848420@nbd.name>
 <caac2b21-d5de-32ac-0fe0-75af8fb80bbb@linuxfoundation.org>
 <878s7nqhg0.fsf@codeaurora.org>
From:   Shuah Khan <skhan@linuxfoundation.org>
Message-ID: <6bbeb37f-620e-d92d-d042-a507bbb39808@linuxfoundation.org>
Date:   Wed, 17 Feb 2021 07:56:55 -0700
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On 2/17/21 12:30 AM, Kalle Valo wrote:
> Shuah Khan <skhan@linuxfoundation.org> writes:
> 
>> On 2/16/21 12:53 AM, Felix Fietkau wrote:
>>>
>>> On 2021-02-16 08:03, Kalle Valo wrote:
>>>> Shuah Khan <skhan@linuxfoundation.org> wrote:
>>>>
>>>>> ath_tx_process_buffer() references ieee80211_find_sta_by_ifaddr()
>>>>> return pointer (sta) outside null check. Fix it by moving the code
>>>>> block under the null check.
>>>>>
>>>>> This problem was found while reviewing code to debug RCU warn from
>>>>> ath10k_wmi_tlv_parse_peer_stats_info() and a subsequent manual audit
>>>>> of other callers of ieee80211_find_sta_by_ifaddr() that don't hold
>>>>> RCU read lock.
>>>>>
>>>>> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
>>>>> Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
>>>>
>>>> Patch applied to ath-next branch of ath.git, thanks.
>>>>
>>>> a56c14bb21b2 ath9k: fix ath_tx_process_buffer() potential null ptr dereference
>>> I just took another look at this patch, and it is completely bogus.
>>> Not only does the stated reason not make any sense (sta is simply passed
>>> to other functions, not dereferenced without checks), but this also
>>> introduces a horrible memory leak by skipping buffer completion if sta
>>> is NULL.
>>> Please drop it, the code is fine as-is.
>>
>> A comment describing what you said here might be a good addition to this
>> comment block though.
> 
> Shuah, can you send a followup patch which reverts your change and adds
> the comment? I try to avoid rebasing my trees.
> 


I can do that.

thanks,
-- Shuah