Re: [patch 1/3 v2] vfio: signedness bug in vfio_config_do_rw()

Alex Williamson
2012-06-28T22:24:29Z

On Thu, 2012-06-28 at 11:07 +0300, Dan Carpenter wrote:
> The "count" variable needs to be signed here because we use it to store
> negative error codes.
>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> v2: Just declare count as signed.
>
> diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
> index a4f7321..2e00aa8 100644
> --- a/drivers/vfio/pci/vfio_pci_config.c
> +++ b/drivers/vfio/pci/vfio_pci_config.c
> @@ -1419,7 +1419,7 @@ void vfio_config_free(struct vfio_pci_device *vdev)
> }
>
> static ssize_t vfio_config_do_rw(struct vfio_pci_device *vdev, char __user *buf,
> - size_t count, loff_t *ppos, bool iswrite)
> + ssize_t count, loff_t *ppos, bool iswrite)
> {
> struct pci_dev *pdev = vdev->pdev;
> struct perm_bits *perm;

signed doesn't seem right for count since just below this chunk we do:

if (*ppos < 0 || *ppos + count > pdev->cfg_size)
return -EFAULT;

So then we have to start testing for negative count. I've added a
ssize_t variable for return that should clear things up. Thanks for the
report!

Alex