I've bisected it down to this commit, introduced in 3.13.0-49.81:
commit b671cf8ede23e76aea4d87d7dc654ee27edaeaf0 Author: Linus Torvalds <email address hidden> Date: Thu Jan 29 11:15:17 2015 -0800
vm: make stack guard page errors return VM_FAULT_SIGSEGV rather than SIGBUS
commit 9c145c56d0c8a0b62e48c8d71e055ad0fb2012ba upstream.
I've bisected it down to this commit, introduced in 3.13.0-49.81:
commit b671cf8ede23e76 aea4d87d7dc654e e27edaeaf0
Author: Linus Torvalds <email address hidden>
Date: Thu Jan 29 11:15:17 2015 -0800
vm: make stack guard page errors return VM_FAULT_SIGSEGV rather than SIGBUS
commit 9c145c56d0c8a0b 62e48c8d71e055a d0fb2012ba upstream.