On Fri, Oct 23, 2020 at 03:08:53PM +0300, Dan Carpenter wrote:
> The copy_to/from_user() functions return the number of bytes which we
> weren't able to copy but the ioctl should return -EFAULT if they fail.
>
> Fixes: a127c5bbb6a8 ("vhost-vdpa: fix backend feature ioctls")
> Signed-off-by: Dan Carpenter <dan.carpen...@oracle.com>
Acked-by: Michael S. Tsirkin <m...@redhat.com>
Needed for stable I guess.
> ---
> drivers/vhost/vdpa.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 62a9bb0efc55..c94a97b6bd6d 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -428,12 +428,11 @@ static long vhost_vdpa_unlocked_ioctl(struct file
> *filep,
> void __user *argp = (void __user *)arg;
> u64 __user *featurep = argp;
> u64 features;
> - long r;
> + long r = 0;
>
> if (cmd == VHOST_SET_BACKEND_FEATURES) {
> - r = copy_from_user(&features, featurep, sizeof(features));
> - if (r)
> - return r;
> + if (copy_from_user(&features, featurep, sizeof(features)))
> + return -EFAULT;
> if (features & ~VHOST_VDPA_BACKEND_FEATURES)
> return -EOPNOTSUPP;
> vhost_set_backend_features(&v->vdev, features);
> @@ -476,7 +475,8 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
> break;
> case VHOST_GET_BACKEND_FEATURES:
> features = VHOST_VDPA_BACKEND_FEATURES;
> - r = copy_to_user(featurep, &features, sizeof(features));
> + if (copy_to_user(featurep, &features, sizeof(features)))
> + r = -EFAULT;
> break;
> default:
> r = vhost_dev_ioctl(&v->vdev, cmd, argp);
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