vfio-mdev: return -EFAULT if copy_to_user() fails

The copy_to_user() function returns the number of bytes which it wasn't
able to copy but we want to return a negative error code.

Fixes: 9d1a546c53b4 ("docs: Sample driver to demonstrate how to use Mediated device framework.")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Kirti Wankhede <kwankhede@nvidia.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

1 files changed, 12 insertions, 3 deletions

diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
index 1fc57a5093a7..975af5bbf28d 100644
--- a/samples/vfio-mdev/mtty.c
+++ b/samples/vfio-mdev/mtty.c
@@ -1180,7 +1180,10 @@ static long mtty_ioctl(struct mdev_device *mdev, unsigned int cmd,
 
                 memcpy(&mdev_state->dev_info, &info, sizeof(info));
 
-                return copy_to_user((void __user *)arg, &info, minsz);
+                if (copy_to_user((void __user *)arg, &info, minsz))
+                        return -EFAULT;
+
+                return 0;
         }
         case VFIO_DEVICE_GET_REGION_INFO:
         {
@@ -1201,7 +1204,10 @@ static long mtty_ioctl(struct mdev_device *mdev, unsigned int cmd,
                 if (ret)
                         return ret;
 
-                return copy_to_user((void __user *)arg, &info, minsz);
+                if (copy_to_user((void __user *)arg, &info, minsz))
+                        return -EFAULT;
+
+                return 0;
         }
 
         case VFIO_DEVICE_GET_IRQ_INFO:
@@ -1224,7 +1230,10 @@ static long mtty_ioctl(struct mdev_device *mdev, unsigned int cmd,
                 if (info.count == -1)
                         return -EINVAL;
 
-                return copy_to_user((void __user *)arg, &info, minsz);
+                if (copy_to_user((void __user *)arg, &info, minsz))
+                        return -EFAULT;
+
+                return 0;
         }
         case VFIO_DEVICE_SET_IRQS:
         {