linux-kernel - Re: selinux vs devtmpfs (vs udev)

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Date:	Mon, 30 Aug 2010 19:14:30 -0400
From:	Eric Paris <eparis@...hat.com>
To:	Kay Sievers <kay.sievers@...y.org>
Cc:	linux-kernel@...r.kernel.org, selinux@...ho.nsa.gov,
	greg@...ah.com, sds@...ho.nsa.gov, harald@...hat.com,
	dwalsh@...hat.com
Subject: Re: selinux vs devtmpfs (vs udev)

On Sat, 2010-08-28 at 11:57 +0200, Kay Sievers wrote:
> On Sat, Aug 28, 2010 at 01:00, Eric Paris <eparis@...hat.com> wrote:

> > In the new new days of devtmpfs things aren't as nice.  The kernel is
> > magically creating files in /dev.  These are getting created with the
> > 'default' SELinux context.  So herein lies the problem.
> >
> > The first program that tries to access these files get denied by
> > SELinux.  Now udev actually has logic in it to fix the label on any
> > closed device file, so udev will at that point swoop in, fix the label,
> > and the next program that tries to use the file will work just fine.  Oh
> > fun!

> Udev should still label all device nodes, even when they are created
> by the kernel. Devtmpfs or not should not make a difference here.
> 
> I guess it's a udev bug introduced with:
>   http://git.kernel.org/?p=linux/hotplug/udev.git;a=commitdiff;h=578cc8a8085a47c963b5940459e475ac5f07219c
> 
> and we just need to fix that.

Looks like the likely cause.  I see a note in one of the bugzillas that
says:

Aug 30 14:03:09 pippin udevd-work[347]: preserve file '/dev/dri/card0',
because it has correct dev_t

Which is certainly the part of code in question.  Do you have a quick
fix in mind that you plan to push upstream or should I ask the RH udev
guy to come up with something?

-Eric

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