netdev - RE: [PATCH net] ipv6: sctp: clone options to avoid use after free

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Date:	Thu, 10 Dec 2015 12:26:10 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Daniel Borkmann' <daniel@...earbox.net>,
	Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
	'Eric Dumazet' <eric.dumazet@...il.com>
CC:	Eric Dumazet <edumazet@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>,
	netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Vlad Yasevich <vyasevich@...il.com>,
	Neil Horman <nhorman@...driver.com>,
	"linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org>,
	syzkaller <syzkaller@...glegroups.com>,
	Kostya Serebryany <kcc@...gle.com>,
	"Alexander Potapenko" <glider@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>
Subject: RE: [PATCH net] ipv6: sctp: clone options to avoid use after free

From: Daniel Borkmann
> Sent: 09 December 2015 19:19
> On 12/09/2015 06:11 PM, Marcelo Ricardo Leitner wrote:
> > Em 09-12-2015 14:31, David Laight escreveu:
> >> From: Eric Dumazet [mailto:eric.dumazet@...il.com]
> >>> Sent: 09 December 2015 16:00
> >>> On Wed, 2015-12-09 at 15:49 +0000, David Laight wrote:
> >>>>> SCTP is lacking proper np->opt cloning at accept() time.
> >>>>>
> >>>>> TCP and DCCP use ipv6_dup_options() helper, do the same in SCTP.
> >>>>>
> >>>>> We might later factorize this code in a common helper to avoid
> >>>>> future mistakes.
> >>>>
> >>>> I'm wondering what the real impact of this and the other recent
> >>>> SCTP bugs/patches is on real workloads?
> >>>> We have enough trouble getting our customers to use kernels
> >>>> later that the 2.6.18 based RHEL5 - without having to persuade
> >>>> them to use kernels that contain very recent fixes.
> >>>
> >>> It all depends if your customers let (hostile ?) people run programs on
> >>> the boxes.
> >>
> >> If they require hostile programs I'm not worried.
> >
> > Not really "require", but "allow", as in: allowing third-party applications to run on it.
> 
> Yeah :/ given distros enable almost everything anyway, the first unpriv'ed
> socket(..., IPPROTO_SCTP) call auto-loads SCTP module. But to be honest, I'd
> be surprised if Cloud providers allow for this. Most of this might only run
> on dedicated boxes with telco appliances.

Yes, I'm worried about whether our M3UA code is likely to crash customer
systems, not whether hostile applications can crash it.
These boxes ought to be on private networks since the sigtran protocols
themselves have nothing that even gives a hint of security.

	David