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>

1 files changed, 7 insertions, 7 deletions

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index aa88911c9504..0f41c9195e9b 100644
--- 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);