diff --git a/fs/cachefiles/bind.c b/fs/cachefiles/bind.c
index dfb14db..38bb776 100644
--- a/fs/cachefiles/bind.c
+++ b/fs/cachefiles/bind.c
@@ -118,6 +118,12 @@
 	cache->mnt = path.mnt;
 	root = path.dentry;
 
+	ret = -EINVAL;
+	if (mnt_user_ns(path.mnt) != &init_user_ns) {
+		pr_warn("File cache on idmapped mounts not supported");
+		goto error_unsupported;
+	}
+
 	/* check parameters */
 	ret = -EOPNOTSUPP;
 	if (d_is_negative(root) ||