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

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Date:   Wed, 17 Feb 2021 09:30:55 +0200
From:   Kalle Valo <kvalo@...eaurora.org>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     Felix Fietkau <nbd@....name>, davem@...emloft.net, kuba@...nel.org,
        ath9k-devel@....qualcomm.com, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] ath9k: fix ath_tx_process_buffer() potential null ptr dereference

Shuah Khan <skhan@...uxfoundation.org> writes:

> 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.

Shuah, can you send a followup patch which reverts your change and adds
the comment? I try to avoid rebasing my trees.

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