linux-kernel - Re: [PATCH 3.12 28/88] netfilter: x_tables: validate targets of jumps

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Message-ID: <20160725054525.GA8749@unicorn.suse.cz>
Date:	Mon, 25 Jul 2016 07:45:25 +0200
From:	Michal Kubecek <mkubecek@...e.cz>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	Greg KH <greg@...ah.com>, Jiri Slaby <jirislaby@...il.com>,
	stable@...r.kernel.org, linux-kernel@...r.kernel.org,
	Florian Westphal <fw@...len.de>,
	Pablo Neira Ayuso <pablo@...filter.org>
Subject: Re: [PATCH 3.12 28/88] netfilter: x_tables: validate targets of jumps

On Thu, Jul 21, 2016 at 09:00:33PM +0200, Jiri Slaby wrote:
> On 07/21/2016, 08:56 PM, Greg KH wrote:
> > On Thu, Jul 21, 2016 at 08:36:18AM +0200, Jiri Slaby wrote:
> >> On 07/14/2016, 10:15 AM, Jiri Slaby wrote:
> >>> From: Florian Westphal <fw@...len.de>
> >>>
> >>> 3.12-stable review patch.  If anyone has any objections, please let me know.
> >>>
> >>> ===============
> >>>
> >>> commit 36472341017529e2b12573093cc0f68719300997 upstream.
> >>
> >> I am now dropping this one. 3.12.62 will be released without that patch.
> >> After the performance issue is resolved, it will be requeued.
> > 
> > Personally, I think the bug fixes were more important than the
> > performance issues at this point in time, but it's your call to make :)
> 
> Ok, but to quote [1]:
> iptables-restore will take forever (gave up after 10 minutes)
> 
> I would say it proved itself not to be a performance issue, but rather a
> functional issue :). Both Pablo and Florian suggested to postpone the patch.

Even worse: because of a shared lock which is held for all this time,
this allows (on kernel >= 3.8) an unprivileged user to block similar
operation in all network namespaces including init_net.

While a partial DoS like this is certainly better than allowing to crash
the system, it could still be considered a security issue.

Michal Kubecek