api: fix buffer overflow in vl_msg_replay_json

cJSON_Parse() and vlib_cli_output() expect a NULL-terminated C-string.

Type: fix
Fixes: 36217e3ca8

Change-Id: Id9819314fcd332c6076d1330b3433885fff07e36
Signed-off-by: Benoît Ganne <bganne@cisco.com>

src/vlibmemory/vlib_api_cli.c

@@ -785,6 +785,10 @@ vl_msg_read_file (FILE *f)
   while ((n = fread (buf, 1, bufsize, f)))
     vec_add (v, buf, n);
 
+  /* most callers expect a NULL-terminated C-string */
+  if (v)
+    vec_add1 (v, 0);
+
   return v;
 }