On 14.04 with LTS Enablement Stack I can confirm that 4.4.0-108 was broken in the described way (trap on kfree) and 4.4.0-109 works.
On 14.04 with LTS Enablement Stack I can confirm that 4.4.0-108 was broken in the described way (trap on kfree) and 4.4.0-109 works.