Stored procedures are owned by the creator, and are part of the schema of the creator. Users who need to run stored procedures in other schemas must be granted the EXECUTE privilege on the procedure:
GRANT EXECUTE ON procedure_name TO { USER | ROLE };
For the complete syntax of the GRANT statement, see GRANT.
All database objects accessed within the granted procedure, even subsequently called procedures, are accessed according to the rights of the owner of the procedure. No special privileges are necessary.
Since the procedure is run with the privileges of the creator, the procedure not only has the same rights to access objects such as tables, but also uses the schema and catalog of the creator. For example, suppose that USER-2 runs a procedure that was created by USER-1. If both users have a table named TABLE1 then, by default, the stored procedure uses the TABLE1 table that is in the schema that belongs to USER-1.