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

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" [off-list ref] wrote:

quoted

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 <redacted>
Cc: stable@vger.kernel.org
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 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