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Subject: Re: [PATCH 2/2] vfio/fsl-mc: prevent underflow in vfio_fsl_mc_mmap()
To:     Dan Carpenter <dan.carpenter@oracle.com>
Cc:     Alex Williamson <alex.williamson@redhat.com>,
        Cornelia Huck <cohuck@redhat.com>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
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From:   Diana Craciun OSS <diana.craciun@oss.nxp.com>
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Acked-by: Diana Craciun <diana.craciun@oss.nxp.com>

On 10/23/2020 2:29 PM, Dan Carpenter wrote:
> My static analsysis tool complains that the "index" can be negative.
> There are some checks in do_mmap() which try to prevent underflows but
> I don't know if they are sufficient for this situation.  Either way,
> making "index" unsigned is harmless so let's do it just to be safe.
> 
> Fixes: 67247289688d ("vfio/fsl-mc: Allow userspace to MMAP fsl-mc device MMIO regions")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
>   drivers/vfio/fsl-mc/vfio_fsl_mc.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/fsl-mc/vfio_fsl_mc.c b/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> index 21f22e3da11f..f27e25112c40 100644
> --- a/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> +++ b/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> @@ -472,7 +472,7 @@ static int vfio_fsl_mc_mmap(void *device_data, struct vm_area_struct *vma)
>   {
>   	struct vfio_fsl_mc_device *vdev = device_data;
>   	struct fsl_mc_device *mc_dev = vdev->mc_dev;
> -	int index;
> +	unsigned int index;
>   
>   	index = vma->vm_pgoff >> (VFIO_FSL_MC_OFFSET_SHIFT - PAGE_SHIFT);
>   
>