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

[Kees Cook]

On Mon, Sep 10, 2018 at 3:37 PM, Laura Abbott <labbott@xxxxxxxxxx> 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@xxxxxxxxxx>
> ---
>  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);

>         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?

-Kees

-- 
Kees Cook
Pixel Security