linux-kernel - Re: [Security] [PATCH 00/20] world-writable files in sysfs and debugfs

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Date:	Tue, 15 Mar 2011 10:25:51 -0400
From:	James Bottomley <James.Bottomley@...e.de>
To:	Greg KH <greg@...ah.com>
Cc:	Vasiliy Kulikov <segoon@...nwall.com>, security@...nel.org,
	acpi4asus-user@...ts.sourceforge.net, linux-scsi@...r.kernel.org,
	rtc-linux@...glegroups.com, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, platform-driver-x86@...r.kernel.org,
	open-iscsi@...glegroups.com, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org
Subject: Re: [Security] [PATCH 00/20] world-writable files in sysfs and
 debugfs

On Tue, 2011-03-15 at 07:18 -0700, Greg KH wrote:
> On Tue, Mar 15, 2011 at 07:50:28AM -0400, James Bottomley wrote:
> > On Mon, 2011-03-14 at 20:09 -0700, Greg KH wrote:
> > > There are no capability checks on sysfs files right now, so these all
> > > need to be fixed.
> > 
> > That statement is true but irrelevant, isn't it?  There can't be
> > capabilities within sysfs files because the system that does them has no
> > idea what the capabilities would be.  If there were capabilities checks,
> > they'd have to be in the implementing routines.
> 
> Ah, you are correct, sorry for the misunderstanding.
> 
> > I think the questions are twofold:
> > 
> >      1. Did anyone actually check for capabilities before assuming world
> >         writeable files were wrong?
> 
> I do not think so as the majority (i.e. all the ones that I looked at)
> did no such checks.

OK, as long as someone checked, I'm happy.

> >      2. Even if there aren't any capabilities checks in the implementing
> >         routines, should there be (are we going the separated
> >         capabilities route vs the monolithic root route)?
> 
> I think the general consensus is that we go the monolithic root route
> for sysfs files in that we do not allow them to be world writable.
> 
> Do you have any exceptions that you know of that do these checks?

Heh, I didn't call our security vacillations a dizzying ride for
nothing.  I know the goal once was to try to run a distro without root
daemons (which is what required the capabilities stuff).  I'm actually
trying to avoid the issue ... I just want to make sure that people who
care aren't all moving in different directions.

James


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