Re: [PATCH for-4.5] vfio: fix ioctl error handling

[Michael S. Tsirkin]

On Sun, Feb 28, 2016 at 07:23:22AM -0600, Alex Williamson wrote:
> On Thu, 25 Feb 2016 13:34:43 +0200
> "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote:
> 
> > Calling return copy_to_user(...) in an ioctl will not
> > do the right thing if there's a pagefault:
> > copy_to_user returns the number of bytes not copied
> > in this case.
> > 
> > Fix up vfio to do
> > 	if (copy_to_user(...))
> > 		return -EFAULT;
> > 
> > everywhere.
> > 
> > Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> > ---
> >  drivers/vfio/pci/vfio_pci.c                  | 9 ++++++---
> >  drivers/vfio/platform/vfio_platform_common.c | 9 ++++++---
> >  drivers/vfio/vfio_iommu_type1.c              | 6 ++++--
> >  3 files changed, 16 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> > index 2760a7b..27a727a 100644
> > --- a/drivers/vfio/pci/vfio_pci.c
> > +++ b/drivers/vfio/pci/vfio_pci.c
> > @@ -446,7 +446,8 @@ static long vfio_pci_ioctl(void *device_data,
> >  		info.num_regions = VFIO_PCI_NUM_REGIONS;
> >  		info.num_irqs = VFIO_PCI_NUM_IRQS;
> >  
> > -		return copy_to_user((void __user *)arg, &info, minsz);
> > +		if (copy_to_user((void __user *)arg, &info, minsz))
> > +			return -EFAULT;
> 
> Ok, but where do we return 0 on success now?

Ouch. Thanks for pointing this out. Fixed in v2.

-- 
MST