LXC containers are just great! With LXC and LXD installed, we can set up a clean build environment with a single command:

[root@kurma ktm5j]# lxc launch images:centos/7 kernel01
[root@kurma ktm5j]# lxc exec kernel01 -- /bin/bash            <- Get a shell
[root@kernel01 ~]#                                            <- bam

There's a great article about getting kernel source packages here: https://wiki.centos.org/HowTos/I_need_the_Kernel_Source

And information about the dev/build process: https://wiki.centos.org/HowTos/Custom_Kernel

After modifying the tree, run build:

[user@host SPECS]$ rpmbuild -bb --target=`uname -m` kernel.spec 2> build-err.log | tee build-out.log

To install all kernel-* packages, run:

[root@host]# yum localinstall kernel-*.rpm

For this kernel we want to apply the following patch: https://kernel.ubuntu.com/git/ubuntu/ubuntu-xenial.git/commit?id=0c29f9eb00d76a0a99804d97b9e6aba5d0bf19b3

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 8b2369c..d510975 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1174,6 +1174,7 @@ static struct file_system_type ovl_fs_type = {
 	.name		= "overlay",
 	.mount		= ovl_mount,
 	.kill_sb	= kill_anon_super,
+	.fs_flags	= FS_USERNS_MOUNT,
 };
 MODULE_ALIAS_FS("overlay");

Using the process/information from above, we need to:

1. Obtain kernel source packages
2. Install packages as non-root user
3. Modify the source tree (placed in user home dir)
4. Build new RPM packages with modified source tree

A tarball containing the resulting packages from this build can be found in the software partition: /sw/pkgs/kernel-3.10.0-957.1.3.el7.cs_benchexec.x86_64.tar.xz