The following commit is missing in v4.14 and 4.14.y.

6e6fddc78323 ("bpf: fix panic due to oob in bpf_prog_test_run_skb")

Syzbot reports referenced from the commit message can be found at
https://lkml.org/lkml/2018/7/9/96 and
https://lkml.org/lkml/2018/7/9/470

https://lkml.org/lkml/2018/7/9/96 has a link to a C reproducer that causes the crash on v4.14.