linux-kernel - Re: [PATCHv2] scsi: ibmvscsis: Fix a stringop-overflow warning

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Message-ID: <CAGXu5j+hL2RhKgF5nyncc6uettPOyD=Je6zOf6NxvFO+pR4dsg@mail.gmail.com>
Date:   Tue, 11 Sep 2018 11:27:58 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Laura Abbott <labbott@...hat.com>
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: [PATCHv2] scsi: ibmvscsis: Fix a stringop-overflow warning

On Tue, Sep 11, 2018 at 11:24 AM, Kees Cook <keescook@...omium.org> wrote:
> On Tue, Sep 11, 2018 at 11:05 AM, 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 a single snprintf instead of a strcpy + strcat to handle this
>> cleanly.
>>
>> Signed-off-by: Laura Abbott <labbott@...hat.com>
>
> Reviewed-by: Kees Cook <keescook@...omium.org>
>
> -Kees
>
>> ---
>> v2: Swtich to using snprintf per suggestion of Kees
>> ---
>>  drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c | 3 +--
>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c b/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c
>> index fac377320158..9305440a00a1 100644
>> --- a/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c
>> +++ b/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c
>> @@ -3474,8 +3474,7 @@ static int ibmvscsis_probe(struct vio_dev *vdev,
>>                 vscsi->dds.window[LOCAL].liobn,
>>                 vscsi->dds.window[REMOTE].liobn);
>>
>> -       strcpy(vscsi->eye, "VSCSI ");
>> -       strncat(vscsi->eye, vdev->name, MAX_EYE);
>> +       snprintf(vscsi->eye, sizeof(vscsi->eye), "VSCSI%s", vdev->name);

Eek. No, I take it back: Nick Desaulniers has better eyes than me and
pointed out that there should be a space after VSCSI.

-Kees

>>
>>         vscsi->dds.unit_id = vdev->unit_address;
>>         strncpy(vscsi->dds.partition_name, partition_name,
>> --
>> 2.17.1
>>
>
>
>
> --
> Kees Cook
> Pixel Security



-- 
Kees Cook
Pixel Security