Re: PROBLEM: [Launchpad #1396889] [Lenovo ThinkPad T400] kexec reboot fails

From: Kees Cook
Date: Mon Dec 01 2014 - 17:59:43 EST

On Mon, Dec 1, 2014 at 2:45 PM, MegaBrutal <megabrutal@xxxxxxxxx> wrote:
> 2014-12-01 7:32 GMT+01:00 MegaBrutal <megabrutal@xxxxxxxxx>:
>> [X.] Other notes, patches, fixes, workarounds:
>> Downstream report (Ubuntu Launchpad):
>> With kernel bisection, I've found, the first bad commit is
>> 8ab3820fd5b2896d66da7bb2a906bc382e63e7bc x86, kaslr: Return location
>> from decompress_kernel
>> which introduces KASLR.
>> The problem only presents itself when CONFIG_RANDOMIZE_BASE=y.
>> For workaround, there is a "nokaslr" kernel parameter to disable the
>> feature, even if the kernel was compiled with CONFIG_RANDOMIZE_BASE.
> Need to add: as I tested today, unfortunately the "nokaslr" kernel
> option doesn't work around the bug. If a kernel was compiled with
> CONFIG_RANDOMIZE_BASE, it won't properly kexec on my ThinkPad T400,
> even if the "nokaslr" kernel option is provided!
> This could actually help to find the bug, as whatever bad happens must
> happen before the kernel checks for the presence of the "nokaslr"
> kernel parameter.

I suspect you're encountering a subset of the same problems as
described in this thread:

If you can test those patches, that may help demonstrate their utility.



Kees Cook
Chrome OS Security
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