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From: Richard Weinberger <richard@nod.at>
To: Andi Kleen <andi@firstfloor.org>,
	Shanker Wang <shanker@tuna.tsinghua.edu.cn>
Cc: netdev@vger.kernel.org,
	Hannes Frederic Sowa <hannes@stressinduktion.org>,
	Richard Weinberger <richard.weinberger@gmail.com>,
	Guillaume Nault <g.nault@alphalink.fr>,
	Miao Wang <shankerwangmiao@gmail.com>
Subject: Re: [PATCH] net:ppp: replace too strict capability restriction on opening /dev/ppp
Date: Mon, 20 Jun 2016 08:47:12 +0200	[thread overview]
Message-ID: <57679170.5030406@nod.at> (raw)
In-Reply-To: <87wplkihbp.fsf@tassilo.jf.intel.com>

Am 20.06.2016 um 07:02 schrieb Andi Kleen:
> Shanker Wang <shanker@tuna.tsinghua.edu.cn> writes:
> 
>> This patch removes the check for CAP_NET_ADMIN in the initial namespace
>> when opening /dev/open. Instead, CAP_NET_ADMIN is checked in the user
>> namespace the net namespace was created so that /dev/ppp cat get opened
>> in a unprivileged container.
> 
> Seems dangerous. From a quick look at the PPP ioctl there is no limit
> how many PPP devices this can create. So a container having access to
> this would be able to fill all kernel memory. Probably needs more
> auditing and hardening first.
> 
> In general there seems to be a lot of attack surface for root
> in PPP.

You are right.
Shanker Wang, I had also another at the open function, it is more complicated
than I thought. Please see how ppp_unattached_ioctl() is called.
Before we give containers access to it the use of nsproxy has to be removed.
Not sure how easy this will be, especially since you cannot break existing users.

Thanks,
//richard

  reply	other threads:[~2016-06-20  6:48 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-18 23:38 [PATCH] net:ppp: replace too strict capability restriction on opening /dev/ppp Shanker Wang
2016-06-20  5:02 ` Andi Kleen
2016-06-20  6:47   ` Richard Weinberger [this message]
  -- strict thread matches above, loose matches on Subject: below --
2016-06-19  5:21 Shanker Wang
2016-06-19  5:24 ` David Miller
2016-06-19  5:31   ` Shanker Wang
2016-06-19 10:13 ` Richard Weinberger
2016-06-19 10:36   ` Shanker Wang
2016-06-19 10:40     ` Richard Weinberger
2016-07-16  9:41       ` Shanker Wang

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