linux-kernel - Re: [PATCH][next] scsi: aacraid: Replace one-element array with flexible-array member

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Message-ID: <yq1h7ka7q68.fsf@ca-mkp.ca.oracle.com>
Date:   Tue, 13 Apr 2021 00:52:16 -0400
From:   "Martin K. Petersen" <martin.petersen@...cle.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Adaptec OEM Raid Solutions <aacraid@...rosemi.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] scsi: aacraid: Replace one-element array with
 flexible-array member

Hi Kees/Gustavo!

>> @@ -4020,7 +4020,8 @@ static int aac_convert_sgraw2(struct aac_raw_io2 *rio2, int pages, int nseg, int
>>  		}
>>  	}
>>  	sge[pos] = rio2->sge[nseg-1];
>> -	memcpy(&rio2->sge[1], &sge[1], (nseg_new-1)*sizeof(struct sge_ieee1212));
>> +	memcpy(&rio2->sge[1], &sge[1],
>> +	       flex_array_size(rio2, sge, nseg_new - 1));
>
> This was hard to validate, 

... which is why I didn't apply this patch. I don't like changes which
make the reader have to jump through hoops to figure out what the code
actually does. I find the original much easier to understand.

Silencing analyzer warnings shouldn't be done at the expense of human
readers. If it is imperative to switch to flex_array_size() to quiesce
checker warnings, please add a comment in the code explaining that the
size evaluates to nseg_new-1 sge_ieee1212 structs.

-- 
Martin K. Petersen	Oracle Linux Engineering