linux-kernel - Re: [PATCH v2 for-4.5] vfio: fix ioctl error handling

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Date:	Sun, 28 Feb 2016 16:55:17 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Baptiste Reynal <b.reynal@...tualopensystems.com>,
	Antonios Motakis <a.motakis@...tualopensystems.com>,
	Eric Auger <eric.auger@...aro.org>,
	Julia Lawall <Julia.Lawall@...6.fr>, kvm@...r.kernel.org
Subject: Re: [PATCH v2 for-4.5] vfio: fix ioctl error handling

On Sun, Feb 28, 2016 at 08:33:50AM -0600, Alex Williamson wrote:
> On Sun, 28 Feb 2016 16:25:07 +0200
> "Michael S. Tsirkin" <mst@...hat.com> wrote:
> 
> > On Sun, Feb 28, 2016 at 08:23:36AM -0600, Alex Williamson wrote:
> > > On Sun, 28 Feb 2016 15:51:49 +0200
> > > "Michael S. Tsirkin" <mst@...hat.com> 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;
> > > > 	return 0;
> > > > 
> > > > everywhere.
> > > > 
> > > > Cc: stable@...r.kernel.org
> > > > Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> > > > ---
> > > > 
> > > > Changes from v1:
> > > > 	fix up good path logic to return 0.
> > > > 
> > > > Compiled only.
> > > > 
> > > >  drivers/vfio/pci/vfio_pci.c                  | 12 +++++++++---
> > > >  drivers/vfio/platform/vfio_platform_common.c | 12 +++++++++---
> > > >  drivers/vfio/vfio_iommu_type1.c              |  8 ++++++--
> > > >  3 files changed, 24 insertions(+), 8 deletions(-)
> > > > 
> > > > diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> > > > index 2760a7b..286b91f 100644
> > > > --- a/drivers/vfio/pci/vfio_pci.c
> > > > +++ b/drivers/vfio/pci/vfio_pci.c
> > > > @@ -446,7 +446,9 @@ 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;
> > > > +		return 0;  
> > > 
> > > Any objection to a ternary in each case?
> > > 
> > > 		return copy_to_user((void __user *)arg,
> > > 				    &info, minsz) ? -EFAULT : 0;  
> > 
> > If you prefer, I'll do it in v3.
> 
> Looks clean and compact to me.  Thanks,
> 
> Alex

Does v3 I posted address your comment?

-- 
MST