diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 465df9a..8c6598e 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -828,6 +828,8 @@
 {
 	ssize_t ret;
 
+	if (count == 0)
+		return -EINVAL;
 	if (copy_from_user(kaddr, buf, count))
 		return -EFAULT;
 	kaddr[count] = '\0';