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Subject: Re: [PATCH 2/2] ath9k: fix ath_tx_process_buffer() potential null ptr
 dereference
To:     Felix Fietkau <nbd@nbd.name>, Kalle Valo <kvalo@codeaurora.org>
Cc:     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>
From:   Shuah Khan <skhan@linuxfoundation.org>
Message-ID: <caac2b21-d5de-32ac-0fe0-75af8fb80bbb@linuxfoundation.org>
Date:   Tue, 16 Feb 2021 08:22:07 -0700
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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.

thanks,
-- Shuah