Jackson was a sixth round pick out of Notre Dame.
Update (1:30): DE Jordan Stanton was also added to the squad per reports.
Also signed today were RB Michael Cox, CB Chandler Fenner, WR Julian Talley and tackle Nick Becton, who was waived by San Diego in the cutdown to 75 players on Tuesday.
The Giants still have three open spots to fill.
Update (6:09): OT Rogers Gaines cleared waivers and has been reverted to the team's IR list. More to come on this...