linux-kernel - Re: [PATCH 01/12] Security: Add CAP_COMPROMISE

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Message-ID: <db71c48c-4ec4-4611-935b-bb1b0441112d@email.android.com>
Date:	Wed, 20 Mar 2013 08:03:37 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Matthew Garrett <matthew.garrett@...ula.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-security-module@...r.kernel.org" 
	<linux-security-module@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: [PATCH 01/12] Security: Add CAP_COMPROMISE_KERNEL

CAP_SYS_RAWIO is definitely inappropriate there.

Matthew Garrett <matthew.garrett@...ula.com> wrote:

>On Tue, 2013-03-19 at 18:02 -0700, H. Peter Anvin wrote:
>
>> Looking at it in detail, EVERYTHING in CAP_SYS_RAWIO has the
>possibility
>> of compromising the kernel, because they let device drivers be
>bypassed,
>> which means arbitrary DMA, which means you have everything.
>
>Having checked again, I don't think this is true. The most obvious case
>is libata, which uses CAP_SYS_RAWIO to limit the ability to send raw
>ATA
>commands. Being able to do so clearly permits userspace to avoid any
>kind of policy the vfs has put in place, but there's no obvious way for
>the user to modify the running kernel. Are you suggesting that removing
>the CAP_SYS_RAWIO check there would be reasonable?

-- 
Sent from my mobile phone. Please excuse brevity and lack of formatting.
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