ctdb-daemon: Never use 0 as a client ID

ctdb_control_db_attach() and ctdb_control_db_detach() assume that any
control with client ID 0 comes from another daemon and treat it
specially.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13930

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>

diff --git a/ctdb/server/ctdb_daemon.c b/ctdb/server/ctdb_daemon.c
index c5733bb2592db632b25d4921e30b0fa87e603fe9..acb40bdb8df65eaf6abed7a54ff1f173fea7f24e 100644 (file)
--- a/ctdb/server/ctdb_daemon.c
+++ b/ctdb/server/ctdb_daemon.c
@@ -1051,6 +1051,44 @@ static int ctdb_clientpid_destructor(struct ctdb_client_pid_list *client_pid)
        return 0;
 }
 
+static int get_new_client_id(struct reqid_context *idr,
+                            struct ctdb_client *client,
+                            uint32_t *out)
+{
+       uint32_t client_id;
+
+       client_id = reqid_new(idr, client);
+       /*
+        * Some places in the code (e.g. ctdb_control_db_attach(),
+        * ctdb_control_db_detach()) assign a special meaning to
+        * client_id 0.  The assumption is that if client_id is 0 then
+        * the control has come from another daemon.  Therefore, we
+        * should never return client_id == 0.
+        */
+       if (client_id == 0) {
+               /*
+                * Don't leak ID 0.  This is safe because the ID keeps
+                * increasing.  A test will be added to ensure that
+                * this doesn't change.
+                */
+               reqid_remove(idr, 0);
+
+               client_id = reqid_new(idr, client);
+       }
+
+       if (client_id == REQID_INVALID) {
+               return EINVAL;
+       }
+
+       if (client_id == 0) {
+               /* Every other ID must have been used and we can't use 0 */
+               reqid_remove(idr, 0);
+               return EINVAL;
+       }
+
+       *out = client_id;
+       return 0;
+}
 
 static void ctdb_accept_client(struct tevent_context *ev,
                               struct tevent_fd *fde, uint16_t flags,
@@ -1094,7 +1132,15 @@ static void ctdb_accept_client(struct tevent_context *ev,
 
        client->ctdb = ctdb;
        client->fd = fd;
-       client->client_id = reqid_new(ctdb->idr, client);
+
+       ret = get_new_client_id(ctdb->idr, client, &client->client_id);
+       if (ret != 0) {
+               DBG_ERR("Unable to get client ID (%d)\n", ret);
+               close(fd);
+               talloc_free(client);
+               return;
+       }
+
        client->pid = peer_pid;
 
        client_pid = talloc(client, struct ctdb_client_pid_list);