[ubuntu-hardened] KASLR: enabling on x86 with "kaslr" option via '/etc/default/grub' file.

[daniel curtis]

Hi Seth

I'm sorry, that I'm still writing about KASLR, but there is one thing,
which is confusing me so I want to clear this. There is an article from
2013 on lwn.net website where an interesting thing is written: "The patches
are currently only for 64-bit x86, though Cook plans to look at ARM next."

I'm using x86 architecture and I want to ask if I can enable KASLR via
'/etc/default/grub' file? (Just as I'd mentioned in my first message etc.)

I realize, that my questions are naive etc., but according to an article
written by Mr Brad Spender, KASLR is... a failure. More informations can be
found here [1]. I don't want to describe all the charges against KASLR etc.
I think it's not needed. But there is one issue drawing my attention.

It is; "the amount of randomization that can be applied to the base address
of the kernel image (...)" According to a mentioned article, randomizations
is "rather small", because of "address space size and memory management
hardware constraints" and "a good userland ASLR implementation provides at
least twice the entropy of what we can see in KASLR implementations."

I would like to know your personal opinion etc. Is the KASLR really a
"failure" and it is not worth to use? I'm just asking, because "KASLR: An
Exercise in Cargo Cult Security" article amazed me.

Of course, I will use 'kptr_restrict' and 'dmesg_restrict' all together
with KASLR. So maybe it's not a "failure"? (Tests with KASLR will be done
on a testing machine.)

Seth, I'm sorry for such naive questions :- ( and thanks for your patience.

Best regards.
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[1] https://forums.grsecurity.net/viewtopic.php?f=7&t=3367
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