linux-kernel - Re: [PATCH v2] scsi/cxgbi/libcxgbi: make sure sg is present before calling sg

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Date:   Tue, 15 Nov 2022 10:59:45 -0600
From:   Mike Christie <michael.christie@...cle.com>
To:     Daniil Tatianin <d-tatianin@...dex-team.ru>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>
Cc:     "Martin K. Petersen" <martin.petersen@...cle.com>,
        Lee Duncan <lduncan@...e.com>,
        Nilesh Javali <njavali@...vell.com>, Wu Bo <wubo40@...wei.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        lvc-project@...uxtesting.org, yc-core@...dex-team.ru,
        Varun Prakash <varun@...lsio.com>
Subject: Re: [PATCH v2] scsi/cxgbi/libcxgbi: make sure sg is present before
 calling sg_next()

Cc'ing the cxgbi/t maintainer, Varun.

On 11/15/22 2:17 AM, Daniil Tatianin wrote:
> On 11/15/22 1:23 AM, Mike Christie wrote:
>> On 11/14/22 9:09 AM, Daniil Tatianin wrote:
>>> sg_next() dereferences the passed sg, therefore we have to verify that
>>> it's present before calling it.
>>>
>>> Found by Linux Verification Center (linuxtesting.org) with the SVACE
>>> static analysis tool.
>>>
>>> Signed-off-by: Daniil Tatianin <d-tatianin@...dex-team.ru>
>>> ---
>>>   drivers/scsi/cxgbi/libcxgbi.c | 3 +--
>>>   1 file changed, 1 insertion(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/scsi/cxgbi/libcxgbi.c b/drivers/scsi/cxgbi/libcxgbi.c
>>> index af281e271f88..2ff9810f42a9 100644
>>> --- a/drivers/scsi/cxgbi/libcxgbi.c
>>> +++ b/drivers/scsi/cxgbi/libcxgbi.c
>>> @@ -1196,8 +1196,7 @@ void cxgbi_ddp_set_one_ppod(struct cxgbi_pagepod *ppod,
>>>         if (offset == len) {
>>>           offset = 0;
>>> -        sg = sg_next(sg);
>>> -        if (sg) {
>>> +        if (sg && (sg = sg_next(sg))) {
>>>               addr = sg_dma_address(sg);
>>>               len = sg_dma_len(sg);
>>>           }
>>
>> Is cxgbit_set_one_ppod the same function but it already has the extra
>> sg check?
> 
> Good catch! Certainly looks that way, albeit with messier indentation.
> 
>> Should it be a libcxgb function in libcxgb_ppm.c?
> 
> That makes sense to me. Should I just move both there?

I think you can move one function with a fix to libcxgb and kill the second one.
Name the new function to cxgb_ddp_set_one_ppod then have cxgbi and cxgbt use it.