linux-kernel - Re: [PATCH] devtmpfs: mount with noexec and nosuid

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Message-ID: <CAPXgP12e5LpN6XVxaXOHhH=u8XXN==2reTaJDCoCk4tP4QduDQ@mail.gmail.com>
Date:	Sat, 17 Nov 2012 01:39:02 +0100
From:	Kay Sievers <kay@...y.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org,
	ellyjones@...omium.org
Subject: Re: [PATCH] devtmpfs: mount with noexec and nosuid

On Sat, Nov 17, 2012 at 1:27 AM, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> On Fri, Nov 16, 2012 at 04:20:16PM -0800, Kees Cook wrote:
>> Since devtmpfs is writable, make the default noexec nosuid as well. This
>> protects from the case of a privileged process having an arbitrary file
>> write flaw and an argumentless arbitrary execution (i.e. it would lack
>> the ability to run "mount -o remount,exec,suid /dev"), with a system
>> that already has nosuid,noexec on all other writable mounts.
>>
>> Cc: ellyjones@...omium.org
>> Signed-off-by: Kees Cook <keescook@...omium.org>
>> ---
>>  drivers/base/devtmpfs.c |    6 ++++--
>>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> Have you tested this to verify that it doesn't break anything?
>
> Kay, could this cause any problems that you could think of?

It breaks all sorts of old, possibly outdated, stuff, that does things
like mapping /dev/mem executable. It for sure used to break X drivers,
that fiddle with the BIOS of cards.

Kay
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