diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 44d1ee429eb0..40f9e1a2ebdd 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1955,8 +1955,10 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx,
 	ret = -EFAULT;
 	if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api)))
 		goto out;
-	/* Ignore unsupported features (userspace built against newer kernel) */
-	features = uffdio_api.features & UFFD_API_FEATURES;
+	features = uffdio_api.features;
+	ret = -EINVAL;
+	if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES))
+		goto err_out;
 	ret = -EPERM;
 	if ((features & UFFD_FEATURE_EVENT_FORK) && !capable(CAP_SYS_PTRACE))
 		goto err_out;