Smith was released by Dallas in May after playing 10 games as an undrafted rookie free agent last season. He re-signed Friday, a day after Keith Rivers retired instead of reporting for training camp and Rolando McClain was placed on the physically unable to perform list.
Smith bounced from the active roster to the practice squad last season while the Cowboys were battling injuries to McClain and other linebackers.
McDermott, an undrafted rookie free agent out of Miami, missed the first day of workouts Thursday with an eye infection.
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