Bug preventing booting with an encrypted system drive

[Stuart Burns]

Hi Everyone,

I have found a bug and could do with some help . I did check to see if 
it exists but as far as I can see it does not. I also tried using the 
automated bug reporting tool but that didn't seem to have the required 
options.

I have installed Xubuntu 15 on my HP ProDesk 405 G2 MT tower from DVD 
media. During installation I chose to use the encrypt disk option during 
setup using the wizard. The system installation completed without issue.

Once this was done I manually ran the update tool. It installed a kernel 
update as well as other updates such as Firefox. On reboot however I am 
no longer able to enter my encryption key. I am presented with the 
splash screen that invites me to type in the key and instead of being 
entered in the decryption key screen it writes the text to the upper 
left hand screen and even if I enter the password it will not accept it 
and boot.

I was using a Bluetooth keyboard (Logitech MK700) but on repeating the 
test with a directly plugged in USB keyboard I get the same issue.

The only was to fix the issue and being able to to boot is to choose the 
4.2.0-16 kernel and doing that works fine with no issue with both of  
the keyboards. This setup has 2 monitors attached. One is DisplayPort to 
VGA and one is standard VGA connectors.

Current kernel:

stuart at ProDesk:~$ uname -a
Linux ProDesk 4.2.0-16-generic #19-Ubuntu SMP Thu Oct 8 15:35:06 UTC 
2015 x86_64 x86_64 x86_64 GNU/Linux

The current list of installed kernels is below

stuart at ProDesk:~$ sudo dpkg --list | grep linux-image
ii  linux-image-4.2.0-16-generic 
4.2.0-16.19                                amd64        Linux kernel 
image for version 4.2.0 on 64 bit x86 SMP
ii  linux-image-4.2.0-27-generic 
4.2.0-27.32                                amd64        Linux kernel 
image for version 4.2.0 on 64 bit x86 SMP
ii  linux-image-extra-4.2.0-16-generic 
4.2.0-16.19                                amd64        Linux kernel 
extra modules for version 4.2.0 on 64 bit x86 SMP
ii  linux-image-extra-4.2.0-27-generic 
4.2.0-27.32                                amd64        Linux kernel 
extra modules for version 4.2.0 on 64 bit x86 SMP
ii  linux-image-generic                           4.2.0.27.30

The lscpu output is below if that helps.

stuart at ProDesk:~$ lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                4
On-line CPU(s) list:   0-3
Thread(s) per core:    1
Core(s) per socket:    4
Socket(s):             1
NUMA node(s):          1
Vendor ID:             AuthenticAMD
CPU family:            22
Model:                 48
Model name:            AMD A8-6410 APU with AMD Radeon R5 Graphics
Stepping:              1
CPU MHz:               1000.000
CPU max MHz:           2000.0000
CPU min MHz:           1000.0000
BogoMIPS:              3992.48
Virtualisation:        AMD-V
L1d cache:             32K
L1i cache:             32K
L2 cache:              2048K
NUMA node0 CPU(s):     0-3