linux-kernel - Re: [PATCH v3 1/7] kexec_file: allow to place kexec

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Date: Tue, 21 May 2024 09:58:36 +0800
From: Coiby Xu <coxu@...hat.com>
To: Baoquan He <bhe@...hat.com>
Cc: kexec@...ts.infradead.org, Ondrej Kozina <okozina@...hat.com>, 
	Milan Broz <gmazyland@...il.com>, Thomas Staudt <tstaudt@...ibm.com>, 
	Daniel P . Berrangé <berrange@...hat.com>, Kairui Song <ryncsn@...il.com>, 
	Jan Pazdziora <jpazdziora@...hat.com>, Pingfan Liu <kernelfans@...il.com>, 
	Dave Young <dyoung@...hat.com>, linux-kernel@...r.kernel.org, x86@...nel.org, 
	Dave Hansen <dave.hansen@...el.com>, Vitaly Kuznetsov <vkuznets@...hat.com>, 
	Eric Biederman <ebiederm@...ssion.com>
Subject: Re: [PATCH v3 1/7] kexec_file: allow to place kexec_buf randomly

On Mon, May 20, 2024 at 02:16:43PM +0800, Baoquan He wrote:
>On 04/25/24 at 06:04pm, Coiby Xu wrote:
>> Currently, kexec_buf is placed in order which means for the same
>> machine, the info in the kexec_buf is always located at the same
>> position each time the machine is booted. This may cause a risk for
>> sensitive information like LUKS volume key. Now struct kexec_buf has a
>> new field random which indicates it's supposed to be placed in a random
>> position.
>
>Do you want to randomize the key's position for both kdump and kexec
>rebooting? Assume you only want to do that for kdump. If so, we may need
>to make that more specific in code.

Thanks for the suggestion! Currently, no one has requested this feature
for kexec reboot so yes, I only have kdump in mind. But kdump depends
on kexec thus I'm not sure how we can make it kdump specfic. Do you have
a further suggestion?


>diff --git a/include/linux/kexec.h b/include/linux/kexec.h
>index 060835bb82d5..fc1e20d565d5 100644
>--- a/include/linux/kexec.h
>+++ b/include/linux/kexec.h
>@@ -171,6 +171,7 @@ int kexec_image_post_load_cleanup_default(struct kimage *image);
>  * @buf_min:	The buffer can't be placed below this address.
>  * @buf_max:	The buffer can't be placed above this address.
>  * @top_down:	Allocate from top of memory.
>+ * @random:	Place the buffer at a random position.

How about a comment here saying this is currently only used by kdump.

-- 
Best regards,
Coiby