Нужно ли применять diff, поставляемый с моим исходным кодом ядра Ubuntu?

Проверьте вывод команды, которую Вы выполнили для строк как те, которые полужирным в следующем:

$ apt-get source linux-image-$(uname -r)
Reading package lists... Done
Picking 'linux' as source package instead of 'linux-image-4.4.0-127-generic'
NOTICE: 'linux' packaging is maintained in the 'Git' version control system at:
git://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/xenial
Please use:
git clone git://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/xenial
to retrieve the latest (possibly unreleased) updates to the package.
Need to get 147 MB of source archives.
Get:1 ftp://ftp.iitb.ac.in//os/ubuntu/archives/ubuntu xenial-security/main linux 4.4.0-128.154 (dsc) [9,712 B]
Get:2 ftp://ftp.iitb.ac.in//os/ubuntu/archives/ubuntu xenial-security/main linux 4.4.0-128.154 (tar) [133 MB]
Get:3 ftp://ftp.iitb.ac.in//os/ubuntu/archives/ubuntu xenial-security/main linux 4.4.0-128.154 (diff) [14.5 MB]
Fetched 147 MB in 3s (39.6 MB/s)  
gpgv: Signature made Fri 25 May 2018 19:40:29 IST using RSA key ID CBEECEA3
gpgv: Can't check signature: public key not found
dpkg-source: warning: failed to verify signature on ./linux_4.4.0-128.154.dsc
dpkg-source: info: extracting linux in linux-4.4.0
dpkg-source: info: unpacking linux_4.4.0.orig.tar.gz
dpkg-source: info: applying linux_4.4.0-128.154.diff.gz
dpkg-source: info: upstream files that have been modified: 
 linux-4.4.0/Documentation/ABI/stable/sysfs-bus-vmbus
 linux-4.4.0/Documentation/ABI/testing/debugfs-aufs
 linux-4.4.0/Documentation/ABI/testing/sysfs-aufs
 linux-4.4.0/Documentation/ABI/testing/sysfs-bus-iio-proximity-as3935
 linux-4.4.0/Documentation/ABI/testing/sysfs-bus-usb
 linux-4.4.0/Documentation/ABI/testing/sysfs-class-cxl
 linux-4.4.0/Documentation/ABI/testing/sysfs-devices-system-cpu
 linux-4.4.0/Documentation/ABI/testing/sysfs-kernel-livepatch
...