bpf: check for reserved flag bits in array and stack maps

Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index bd3bdf2..76d5a79 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -53,7 +53,7 @@
 
 	/* check sanity of attributes */
 	if (attr->max_entries == 0 || attr->key_size != 4 ||
-	    attr->value_size == 0)
+	    attr->value_size == 0 || attr->map_flags)
 		return ERR_PTR(-EINVAL);
 
 	if (attr->value_size >= 1 << (KMALLOC_SHIFT_MAX - 1))