linux-kernel - Re: [PATCH] scsi: ses: Handle enclosure with just a primary component gracefully

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Message-ID: <b71bca20-401f-c877-168c-c26ca1c282d1@sangfor.com.cn>
Date:   Wed, 5 Apr 2023 12:27:32 +0800
From:   Ding Hui <dinghui@...gfor.com.cn>
To:     jejb@...ux.ibm.com, Jiri Kosina <jikos@...nel.org>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Michal Kolar <mich.k@...nam.cz>
Subject: Re: [PATCH] scsi: ses: Handle enclosure with just a primary component
 gracefully

On 2023/4/5 4:26, James Bottomley wrote:
> On Tue, 2023-04-04 at 21:23 +0200, Jiri Kosina wrote:
>> From: Jiri Kosina <jkosina@...e.cz>
>>
>> This reverts 3fe97ff3d9493 ("scsi: ses: Don't attach if enclosure has
>> no components") and introduces proper handling of case where there
>> are no detected secondary components, but primary component
>> (enumerated in num_enclosures) does exist. That fix was originally
>> proposed by Ding Hui <dinghui@...gfor.com.cn>.
> 
> I think everything in here looks fine except this:
> 
>> --- a/drivers/scsi/ses.c
>> +++ b/drivers/scsi/ses.c
>> @@ -509,9 +509,6 @@ static int ses_enclosure_find_by_addr(struct
>> enclosure_device *edev,
>>          int i;
>>          struct ses_component *scomp;
>>   
>> -       if (!edev->component[0].scratch)
>> -               return 0;
>> -
>>          for (i = 0; i < edev->components; i++) {
>>                  scomp = edev->component[i].scratch;
>>                  if (scomp->addr != efd->addr)
> 
> If you remove the check, then scomp could be NULL here and we'll oops
> on scomp->addr.

I think we should remove the check, because the edev->components 
represented the effectiveness of array pointers, so we need check 
edev->components firstly instead of checking edev->component[0].scratch, 
if edev->components is 0, we won't enter the for loop, don't worry about 
dereference scomp.

> 
> Regards,
> 
> James
> 
> 

-- 
Thanks,
-dinghui