linux-kernel - Re: [PATCH][next] scsi: hisi_sas: Avoid a couple -Wflex-array-member-not-at-end warnings

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Message-ID: <0e46139a-bb80-4684-977d-aaacc653840b@embeddedor.com>
Date: Tue, 7 Oct 2025 11:54:23 +0100
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 Yihang Li <liyihang9@...artners.com>,
 "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
 "Martin K. Petersen" <martin.petersen@...cle.com>
Cc: linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] scsi: hisi_sas: Avoid a couple
 -Wflex-array-member-not-at-end warnings



On 10/7/25 11:45, Gustavo A. R. Silva wrote:
> Hi all,
> 
> Friendly ping: who can take this, please?
> 
> Thanks!
> -Gustavo
> 
> On 9/19/25 13:17, Gustavo A. R. Silva wrote:
>> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
>> getting ready to enable it, globally.
>>
>> Move the conflicting declarations to the end of the corresponding
>> structures (and in a union). Notice that `struct ssp_command_iu`
>> is a flexible structure, this is a structure that contains a
>> flexible-array member.
>>
>> With these changes fix the following warnings:
>>
>> drivers/scsi/hisi_sas/hisi_sas.h:639:38: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member- 
>> not-at-end]
>> drivers/scsi/hisi_sas/hisi_sas.h:616:47: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member- 
>> not-at-end]
>>
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
>> ---
>>   drivers/scsi/hisi_sas/hisi_sas.h | 10 +++++++---
>>   1 file changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/scsi/hisi_sas/hisi_sas.h b/drivers/scsi/hisi_sas/hisi_sas.h
>> index 1323ed8aa717..55c638dd58b1 100644
>> --- a/drivers/scsi/hisi_sas/hisi_sas.h
>> +++ b/drivers/scsi/hisi_sas/hisi_sas.h
>> @@ -613,8 +613,8 @@ struct hisi_sas_command_table_ssp {
>>       struct ssp_frame_hdr hdr;
>>       union {
>>           struct {
>> -            struct ssp_command_iu task;
>>               u32 prot[PROT_BUF_SIZE];
>> +            struct ssp_command_iu task;
>>           };

Actually, I have a question here:

is u32 prot[PROT_BUF_SIZE]; intended to overlap flex array task.add_cdb[]
at some point?

if not, this change is just fine. Otherwise, I'd need to update this
patch to account for the overlap.

Could someone provide some feedback here? :)

Thanks!
-Gustavo

>>           struct ssp_tmf_iu ssp_task;
>>           struct xfer_rdy_iu xfer_rdy;
>> @@ -636,13 +636,17 @@ struct hisi_sas_status_buffer {
>>   struct hisi_sas_slot_buf_table {
>>       struct hisi_sas_status_buffer status_buffer;
>> -    union hisi_sas_command_table command_header;
>>       struct hisi_sas_sge_page sge_page;
>> +
>> +    /* Must be last --ends in a flexible-array member. */
>> +    union hisi_sas_command_table command_header;
>>   };
>>   struct hisi_sas_slot_dif_buf_table {
>> -    struct hisi_sas_slot_buf_table slot_buf;
>>       struct hisi_sas_sge_dif_page sge_dif_page;
>> +
>> +    /* Must be last --ends in a flexible-array member. */
>> +    struct hisi_sas_slot_buf_table slot_buf;
>>   };
>>   extern struct scsi_transport_template *hisi_sas_stt;
>