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

From: Kalle Valo <[email-masked]>
Date: Mon, 04 May 2020 14:54:13 +0300

"Gustavo A. R. Silva" <[email-masked]> 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 <[email-masked]>
>> ---
>>  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.

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