linux-kernel - Re: [PATCH 04/15] ath10k: fix gcc-10 zero-length-bounds warnings

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Date:   Tue, 05 May 2020 07:56:03 +0300
From:   Kalle Valo <kvalo@...eaurora.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Michal Kazior <michal.kazior@...to.com>,
        Maharaja Kennadyrajan <mkenna@...eaurora.org>,
        Wen Gong <wgong@...eaurora.org>,
        Erik Stromdahl <erik.stromdahl@...il.com>,
        ath10k@...ts.infradead.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH 04/15] ath10k: fix gcc-10 zero-length-bounds warnings

"Gustavo A. R. Silva" <gustavo@...eddedor.com> writes:

> On 5/4/20 06:54, Kalle Valo wrote:
>> "Gustavo A. R. Silva" <gustavo@...eddedor.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@...db.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.

Great, thanks.

-- 
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