vhost_vdpa: Return -EFAULT if copy_from_user() fails

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.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20201023120853.GI282278@mwanda
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Cc: stable@vger.kernel.org
Acked-by: Jason Wang <jasowang@redhat.com>

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 846de69d9c0120329a48233d642e91af2c93e906..37f461cff8925138c23a5ec19b69ec03f84aea33 100644 (file)
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -432,12 +432,11 @@ 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);
@@ -480,7 +479,8 @@ 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;
        case VHOST_VDPA_GET_IOVA_RANGE:
                r = vhost_vdpa_get_iova_range(v, argp);