Stepfunction runs into IAMPassRole error on ECS Runtask

I am trying to make a step function that will start an ECS Fargate container with environment variables from the input. Whenever I try and run the function I get what seems to be an IAMs error, but I made a new IAMs account with the function. So it should have all of the needed permissions, and the account that I am using has nearly full permissions, so I don't know how it could be an IAMs issue.

{
  "Comment": "A description of my state machine",
  "StartAt": "ECS RunTask",
  "States": {
    "ECS RunTask": {
      "Type": "Task",
      "Resource": "arn:aws:states:::ecs:runTask.sync",
      "Parameters": {
        "LaunchType": "FARGATE",
        "TaskDefinition": "arn:aws:ecs:us-east-1:---:task-definition/---",
        "Overrides": {
          "ContainerOverrides": [
            {
              "Name": "pls work",
              "Environment": [
                {
                  "Name": "INPUT",
                  "Value.$": "$.INPUT"
                }
              ]
            }
          ]
        }
      },
      "Next": "Success"
    },
    "Success": {
      "Type": "Succeed"
    }
  }
}

Here is the error that I am running into:

User: arn:aws:sts::---:assumed-role/StepFunctions-MyStateMachine---/--- is not authorized to perform: iam:PassRole on resource: arn:aws:iam::---:role/ecsTaskExecutionRole because no identity-based policy allows the iam:PassRole action (Service: AmazonECS; Status Code: 400; Error Code: AccessDeniedException; Request ID: ---; Proxy: null)