linux-kernel - Re: [PATCH 2/2] ACPI: Override arbitrary ACPI tables via initrd for debugging

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Date:	Mon, 24 Sep 2012 10:21:59 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Thomas Renninger <trenn@...e.de>
Cc:	Len Brown <lenb@...nel.org>, hpa@...or.com,
	initramfs@...r.kernel.org, robert.moore@...el.com,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	yinghai@...nel.org, eric.piel@...mplin-utc.net, vojcek@...n.pl
Subject: Re: [PATCH 2/2] ACPI: Override arbitrary ACPI tables via initrd for
 debugging

> The issue is/was, that root can inject code at runtime which is then
> executed in kernel environment.

Yes there are lots of other ways to do this too. The constraint we use
for it is CAP_SYS_RAWIO. With that capability you can totally do raw
hardware access and the like so requiring it for runtime ACPI updating
and execution is consistent with the security model.

> Afaik there are "security" provisions or say setups, which do
> hide modprobe/insmod and do not allow root to load any kernel drivers 
> or similar.

To do this you have to revoke CAP_SYS_RAWIO.

Alan
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