vhost-net: fix to check the return value of copy_to/from_user() correctly

copy_to/from_user() returns the number of bytes that could not be copied.

So we need to check if it is not zero, and in that case, we should return
the error number -EFAULT rather than directly return the return value from
copy_to/from_user().

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index aa88911..0f41c91 100644 (file)
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -593,17 +593,17 @@ static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
        int r;
        switch (ioctl) {
        case VHOST_NET_SET_BACKEND:
-               r = copy_from_user(&backend, argp, sizeof backend);
-               if (r < 0)
-                       return r;
+               if (copy_from_user(&backend, argp, sizeof backend))
+                       return -EFAULT;
                return vhost_net_set_backend(n, backend.index, backend.fd);
        case VHOST_GET_FEATURES:
                features = VHOST_FEATURES;
-               return copy_to_user(featurep, &features, sizeof features);
+               if (copy_to_user(featurep, &features, sizeof features))
+                       return -EFAULT;
+               return 0;
        case VHOST_SET_FEATURES:
-               r = copy_from_user(&features, featurep, sizeof features);
-               if (r < 0)
-                       return r;
+               if (copy_from_user(&features, featurep, sizeof features))
+                       return -EFAULT;
                if (features & ~VHOST_FEATURES)
                        return -EOPNOTSUPP;
                return vhost_net_set_features(n, features);