Two new "experimental" stable kernels
Greg Kroah-Hartman has released the 4.9.256
and 4.4.256 in order to try to figure out
if there are any user-space problems caused by the overflow of the minor version number for those
stable-kernel series. "With this release, KERNEL_VERSION(4, 9, 256) is the same as KERNEL_VERSION(4, 10, 0).

Nothing in the kernel build itself breaks with this change, but given that this
is a userspace visible change, and some crazy tools (like glibc and gcc) have
logic that checks the kernel version for different reasons, I wanted to do this
release as an 'empty' release to ensure that everything still works
properly." Those who could be affected would be well-advised to
test this change immediately as he plans another 4.9 release in a
week's time.