netdev - Re: [PATCH 2/2] ath9k: fix ath_tx_process_buffer() potential null ptr dereference

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Date:   Tue, 16 Feb 2021 08:22:07 -0700
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Felix Fietkau <nbd@....name>, Kalle Valo <kvalo@...eaurora.org>
Cc:     davem@...emloft.net, kuba@...nel.org, 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 2/2] ath9k: fix ath_tx_process_buffer() potential null ptr
 dereference

On 2/16/21 12:53 AM, Felix Fietkau wrote:
> 
> On 2021-02-16 08:03, Kalle Valo wrote:
>> Shuah Khan <skhan@...uxfoundation.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@...uxfoundation.org>
>>> Signed-off-by: Kalle Valo <kvalo@...eaurora.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