linux-kernel - Re: [PATCH] scsi: ibmvscsis: Fix a stringop-overflow warning

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Date:   Tue, 11 Sep 2018 10:55:29 -0700
From:   Laura Abbott <labbott@...hat.com>
To:     "Bryant G. Ly" <bryantly@...ux.ibm.com>,
        Kees Cook <keescook@...omium.org>
Cc:     "Bryant G. Ly" <bryantly@...ux.vnet.ibm.com>,
        Michael Cyr <mikecyr@...ux.vnet.ibm.com>,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org,
        target-devel <target-devel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Prarit Bhargava <prarit@...hat.com>
Subject: Re: [PATCH] scsi: ibmvscsis: Fix a stringop-overflow warning

On 09/11/2018 07:34 AM, Bryant G. Ly wrote:
> On 9/10/18 6:30 PM, Kees Cook wrote:
> 
>> On Mon, Sep 10, 2018 at 3:37 PM, Laura Abbott <labbott@...hat.com> wrote:
>>> There's currently a warning about string overflow with strncat:
>>>
>>> drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c: In function 'ibmvscsis_probe':
>>> drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c:3479:2: error: 'strncat' specified
>>> bound 64 equals destination size [-Werror=stringop-overflow=]
>>>    strncat(vscsi->eye, vdev->name, MAX_EYE);
>>>    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>
>>> Switch to using strlcat which correctly accounts for lengths that
>>> are equal to the destination buffer.
>>>
>>> Signed-off-by: Laura Abbott <labbott@...hat.com>
>>> ---
>>>   drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c b/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c
>>> index fac377320158..53d344d8dc43 100644
>>> --- a/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c
>>> +++ b/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c
>>> @@ -3475,7 +3475,7 @@ static int ibmvscsis_probe(struct vio_dev *vdev,
>>>                  vscsi->dds.window[REMOTE].liobn);
>>>
>>>          strcpy(vscsi->eye, "VSCSI ");
>>> -       strncat(vscsi->eye, vdev->name, MAX_EYE);
>>> +       strlcat(vscsi->eye, vdev->name, MAX_EYE);
>> Can this just get switched to snprintf() instead?
>>
>> snprintf(vscsi->eye, sizeof(vscsi->eye), "VSCSI%s", vdev->name);
> 
> Either works for me.
> 

I'll switch to the snprintf since that's cleaner.

>>
>>>          vscsi->dds.unit_id = vdev->unit_address;
>>>          strncpy(vscsi->dds.partition_name, partition_name,
>> And does this strncpy need a NUL-termination and/or trailing padding?
>>
> Yes, good catch, it does need NUL-termination.
> 

I can send that cleanup in a second patch.

> -Bryant
> 
>