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Subject: Re: [PATCH 4/4] x86,module: Detect CRn and DRn manipulation
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Steven Rostedt <rostedt@goodmis.org>, tglx@linutronix.de,
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        Wolfgang Mauerer <wolfgang.mauerer@oth-regensburg.de>
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From:   Jan Kiszka <jan.kiszka@siemens.com>
Message-ID: <3751b1d5-113e-4a5c-da3b-fd1afbdba2ae@siemens.com>
Date:   Wed, 8 Apr 2020 12:50:17 +0200
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On 08.04.20 11:13, Peter Zijlstra wrote:
> On Wed, Apr 08, 2020 at 10:51:38AM +0200, Peter Zijlstra wrote:
>> On Wed, Apr 08, 2020 at 07:58:53AM +0200, Jan Kiszka wrote:
>>> On 07.04.20 23:48, Steven Rostedt wrote:
>>
>>>> Hmm, wont this break jailhouse?
>>
>> Breaking it isn't a problem, it's out of tree and it should be fixable.
>>
>>> Yes, possibly. We load the hypervisor binary via request_firmware into
>>> executable memory and then jump into it. So most of the "suspicious" code is
>>
>> W.T.H. does the firmware loader have the ability to give executable
>> memory? We need to kill that too. /me goes find.
> 
> AFAICT the firmware loader only provides PAGE_KERNEL_RO, so how do you
> get it executable?

memcpy(ioremapped_exec_region, firmware_image)

We only use the loader for getting the blob, not for running it. It has 
to be put at a location that Linux will lose control over anyway.

> 
> I'm thinking the patches Christoph has lined up will take care of this.
> 

It would make sense from a certain POV...

Jan

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