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

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Date:	Tue, 3 Nov 2015 12:25:45 +0100
From:	Quentin Casasnovas <quentin.casasnovas@...cle.com>
To:	santosh shilimkar <santosh.shilimkar@...cle.com>
Cc:	Quentin Casasnovas <quentin.casasnovas@...cle.com>,
	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 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

Quentin
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