lib-smtp: client: Make smtp_client_connection_commands_fail_reply() m…

…ore reliable by copying the command lists.

Copy the current lists of queued and waiting commands and reference each command before calling smtp_client_command_fail_reply().
Failing one command can cause other dependent commands to be aborted (in a transaction or from submission service), which could have caused trouble in this function.
Problems would likely occur at connection disconnect.

src/lib-smtp/smtp-client-command.c

@@ -313,6 +313,37 @@ void smtp_client_command_fail(struct smtp_client_command **_cmd,
 	smtp_client_command_fail_reply(_cmd, &reply);
 }
 
+void smtp_client_commands_list_fail_reply(
+	struct smtp_client_command *cmds_list, unsigned int cmds_list_count,
+	const struct smtp_reply *reply)
+{
+	struct smtp_client_command *cmd;
+	ARRAY(struct smtp_client_command *) cmds_arr;
+	struct smtp_client_command **cmds;
+	unsigned int count, i;
+
+	if (cmds_list == NULL)
+		return;
+	i_assert(cmds_list_count > 0);
+
+	/* copy the array and reference the commands to be robust against more
+	   than one command disappearing from the list */
+	t_array_init(&cmds_arr, cmds_list_count);
+	for (cmd = cmds_list; cmd != NULL; cmd = cmd->next) {
+		smtp_client_command_ref(cmd);
+		array_append(&cmds_arr, &cmd, 1);
+	}
+
+	cmds = array_get_modifiable(&cmds_arr, &count);
+	for (i = 0; i < count; i++) {
+		cmd = cmds[i];
+		/* fail the reply */
+		smtp_client_command_fail_reply(&cmds[i], reply);
+		/* drop our reference */
+		smtp_client_command_unref(&cmd);
+	}
+}
+
 void smtp_client_command_set_abort_callback(struct smtp_client_command *cmd,
 	void (*callback)(void *context), void *context)
 {

src/lib-smtp/smtp-client-connection.c

@@ -145,23 +145,10 @@ static void
 smtp_client_connection_commands_fail_reply(struct smtp_client_connection *conn,
 	const struct smtp_reply *reply)
 {
-	struct smtp_client_command *cmd, *cmd_next = NULL;
-
-	cmd = conn->cmd_wait_list_head;
-	while (cmd != NULL) {
-		i_assert(conn->cmd_wait_list_count > 0);
-		cmd_next = cmd->next;
-		smtp_client_command_fail_reply(&cmd, reply);
-		cmd = cmd_next;
-	}
-
-	cmd = conn->cmd_send_queue_head;
-	while (cmd != NULL) {
-		i_assert(conn->cmd_send_queue_count > 0);
-		cmd_next = cmd->next;
-		smtp_client_command_fail_reply(&cmd, reply);
-		cmd = cmd_next;
-	}
+	smtp_client_commands_list_fail_reply(conn->cmd_wait_list_head,
+					     conn->cmd_wait_list_count, reply);
+	smtp_client_commands_list_fail_reply(conn->cmd_send_queue_head,
+					     conn->cmd_send_queue_count, reply);
 }
 
 static void

src/lib-smtp/smtp-client-private.h

@@ -189,10 +189,14 @@ int smtp_client_command_send_more(struct smtp_client_connection *conn,
 				  const char **error_r);
 int smtp_client_command_input_reply(struct smtp_client_command *cmd,
 				    const struct smtp_reply *reply);
+
 void smtp_client_command_fail(struct smtp_client_command **_cmd,
 			      unsigned int status, const char *error);
 void smtp_client_command_fail_reply(struct smtp_client_command **_cmd,
 				    const struct smtp_reply *reply);
+void smtp_client_commands_list_fail_reply(
+	struct smtp_client_command *cmds_list, unsigned int cmds_list_count,
+	const struct smtp_reply *reply);
 
 /*
  * Transaction