Hey @Hatim,
Add the following statement to the permissions policy for the IAM entity that needs to edit the description of a service-linked role:
{
"Effect": "Allow",
"Action": [
"iam:UpdateRoleDescription"
],
"Resource": "arn:aws:iam::*:role/aws-service-role/ecs.amazonaws.com/AWSServiceRoleForECS*",
"Condition": {"StringLike": {"iam:AWSServiceName": "ecs.amazonaws.com"}}
}