linux-kernel - Re: [PATCH] RDS: fix race condition when sending a message on unbound socket.

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Date:	Tue, 24 Nov 2015 18:25:47 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Quentin Casasnovas <quentin.casasnovas@...cle.com>,
	santosh shilimkar <santosh.shilimkar@...cle.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Vegard Nossum <vegard.nossum@...cle.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Chien Yen <chien.yen@...cle.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] RDS: fix race condition when sending a message on
 unbound socket.

On Tue, 2015-11-03 at 12:25 +0100, Quentin Casasnovas wrote:
> On Fri, Oct 16, 2015 at 10:47:49AM -0700, santosh shilimkar wrote:
> > On 10/16/2015 8:11 AM, Quentin Casasnovas wrote:
> > > Sasha's found a NULL pointer dereference in the RDS connection code when
> > > sending a message to an apparently unbound socket.  The problem is caused
> > > by the code checking if the socket is bound in rds_sendmsg(), which checks
> > > the rs_bound_addr field without taking a lock on the socket.  This opens a
> > > race where rs_bound_addr is temporarily set but where the transport is not
> > > in rds_bind(), leading to a NULL pointer dereference when trying to
> > > dereference 'trans' in __rds_conn_create().
> > > 
> > > Vegard wrote a reproducer for this issue, so kindly ask him to share if
> > > you're interested.
> > > 
> > > I cannot reproduce the NULL pointer dereference using Vegard's reproducer
> > > with this patch, whereas I could without.
> > > 
> > > Complete earlier incomplete fix to CVE-2015-6937:
> > > 
> > >    74e98eb08588 ("RDS: verify the underlying transport exists before creating a connection")
> > > 
> 
> For reference, this has been assigned CVE-2015-7990 on the oss-sec thread:
> 
>   http://seclists.org/oss-sec/2015/q4/179

But the patch doesn't seem to have gone anywhere.  Santosh, can you
apply this in your tree and ask David to pull, or should Quentin re-
send it to netdev?

Ben.

-- 
Ben Hutchings
Unix is many things to many people,
but it's never been everything to anybody.
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