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To:     Kalle Valo <kvalo@codeaurora.org>
Cc:     Arnd Bergmann <arnd@arndb.de>, linux-kernel@vger.kernel.org,
        "David S. Miller" <davem@davemloft.net>,
        Michal Kazior <michal.kazior@tieto.com>,
        Maharaja Kennadyrajan <mkenna@codeaurora.org>,
        Wen Gong <wgong@codeaurora.org>,
        Erik Stromdahl <erik.stromdahl@gmail.com>,
        ath10k@lists.infradead.org, linux-wireless@vger.kernel.org,
        netdev@vger.kernel.org, Kees Cook <keescook@chromium.org>
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From:   "Gustavo A. R. Silva" <gustavo@embeddedor.com>
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Subject: Re: [PATCH 04/15] ath10k: fix gcc-10 zero-length-bounds warnings
Message-ID: <69f5c551-01ab-3b90-01a1-42514cd58f60@embeddedor.com>
Date:   Mon, 4 May 2020 11:09:21 -0500
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On 5/4/20 06:54, Kalle Valo wrote:
> "Gustavo A. R. Silva" <gustavo@embeddedor.com> writes:
> 
>> Hi Arnd,
>>
>> On 4/30/20 16:30, Arnd Bergmann wrote:
>>> gcc-10 started warning about out-of-bounds access for zero-length
>>> arrays:
>>>
>>> In file included from drivers/net/wireless/ath/ath10k/core.h:18,
>>>                  from drivers/net/wireless/ath/ath10k/htt_rx.c:8:
>>> drivers/net/wireless/ath/ath10k/htt_rx.c: In function 'ath10k_htt_rx_tx_fetch_ind':
>>> drivers/net/wireless/ath/ath10k/htt.h:1683:17: warning: array subscript 65535 is outside the bounds of an interior zero-length array 'struct htt_tx_fetch_record[0]' [-Wzero-length-bounds]
>>>  1683 |  return (void *)&ind->records[le16_to_cpu(ind->num_records)];
>>>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>> drivers/net/wireless/ath/ath10k/htt.h:1676:29: note: while referencing 'records'
>>>  1676 |  struct htt_tx_fetch_record records[0];
>>>       |                             ^~~~~~~
>>>
>>> The structure was already converted to have a flexible-array member in
>>> the past, but there are two zero-length members in the end and only
>>> one of them can be a flexible-array member.
>>>
>>> Swap the two around to avoid the warning, as 'resp_ids' is not accessed
>>> in a way that causes a warning.
>>>
>>> Fixes: 3ba225b506a2 ("treewide: Replace zero-length array with flexible-array member")
>>> Fixes: 22e6b3bc5d96 ("ath10k: add new htt definitions")
>>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>>> ---
>>>  drivers/net/wireless/ath/ath10k/htt.h | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/net/wireless/ath/ath10k/htt.h b/drivers/net/wireless/ath/ath10k/htt.h
>>> index e7096a73c6ca..7621f0a3dc77 100644
>>> --- a/drivers/net/wireless/ath/ath10k/htt.h
>>> +++ b/drivers/net/wireless/ath/ath10k/htt.h
>>> @@ -1673,8 +1673,8 @@ struct htt_tx_fetch_ind {
>>>  	__le32 token;
>>>  	__le16 num_resp_ids;
>>>  	__le16 num_records;
>>> -	struct htt_tx_fetch_record records[0];
>>> -	__le32 resp_ids[]; /* ath10k_htt_get_tx_fetch_ind_resp_ids() */
>>> +	__le32 resp_ids[0]; /* ath10k_htt_get_tx_fetch_ind_resp_ids() */
>>> +	struct htt_tx_fetch_record records[];
>>>  } __packed;
>>>  
>>>  static inline void *
>>>
>>
>> The treewide patch is an experimental change and, as this change only applies
>> to my -next tree, I will carry this patch in it, so other people don't have
>> to worry about this at all.
> 
> Gustavo, why do you have ath10k patches in your tree? I prefer that
> ath10k patches go through my ath.git tree so that they are reviewed and
> tested.
> 

I just wanted to test out a mechanical change. I will remove it from my tree
now and will send a patch to you so you can apply it to your ath.git tree.

Thanks!
--
Gustavo