linux-kernel - Re: [PATCH 1/1] devices cgroup: allow mkfifo

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Date:	Thu, 11 Dec 2008 08:59:57 -0600
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Daniel Lezcano <dlezcano@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/1] devices cgroup: allow mkfifo

Quoting Li Zefan (lizf@...fujitsu.com):
> CC: Andrew
> 
> Serge E. Hallyn wrote:
> > The devcgroup_inode_permission() hook in the devices whitelist
> > cgroup has always bypassed access checks on fifos.  But the
> > mknod hook did not.  The devices whitelist is only about block
> > and char devices, and fifos can't even be added to the whitelist,
> > so fifos can't be created at all except by tasks which have 'a'
> > in their whitelist (meaning they have access to all devices).
> > 
> > Fix the behavior by bypassing access checks to mkfifo.
> > 
> 
> It also bypasses checks to mksock. Should backport this patch?

Do you mean push it into -stable?

Couldn't hurt, but it's a DOS to root in a container, not a security
vulnerability, and since noone has complainted until now so at least
it's not panick-worthy.

> Reviewed-by: Li Zefan <lizf@...fujitsu.com>

Thanks.  I'll go ahead and send to Linus and -stable.

-serge

> > Signed-off-by: Serge E. Hallyn <serue@...ibm.com>
> > ---
> >  security/device_cgroup.c |    3 +++
> >  1 files changed, 3 insertions(+), 0 deletions(-)
> > 
> > diff --git a/security/device_cgroup.c b/security/device_cgroup.c
> > index 5ba7870..df9d491 100644
> > --- a/security/device_cgroup.c
> > +++ b/security/device_cgroup.c
> > @@ -513,6 +513,9 @@ int devcgroup_inode_mknod(int mode, dev_t dev)
> >  	struct dev_cgroup *dev_cgroup;
> >  	struct dev_whitelist_item *wh;
> >  
> > +	if (!S_ISBLK(mode) && !S_ISCHR(mode))
> > +		return 0;
> > +
> >  	rcu_read_lock();
> >  
> >  	dev_cgroup = task_devcgroup(current);
--
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