From: Daniel J Walsh <dwalsh@redhat.com>
To: Eric Paris <eparis@parisplace.org>
Cc: Martin Orr <martin@martinorr.name>, selinux@tycho.nsa.gov
Subject: Re: What is /selinux/null?
Date: Wed, 20 Jul 2011 08:58:16 -0400 [thread overview]
Message-ID: <4E26D0E8.2010505@redhat.com> (raw)
In-Reply-To: <CACLa4ps4iGtD0Ov_01V+jxsd=NuFc_C2on74Haxd-M1O35ndaQ@mail.gmail.com>
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On 07/19/2011 09:31 PM, Eric Paris wrote:
> On Tue, Jul 19, 2011 at 5:46 PM, Martin Orr <martin@martinorr.name>
> wrote:
>> Can anyone explain the following AVC denial? What is the purpose
>> of /selinux/null and why would ifconfig open it instead of
>> /dev/null?
>>
>> type=1400 audit(1311107387.404:18): avc: denied { use } for
>> pid=2211 comm="wpa_supplicant" path="/null" dev=selinuxfs ino=22
>> scontext=system_u:system_r:NetworkManager_t:s0
>> tcontext=system_u:system_r:ifconfig_t:s0 tclass=fd
>
> That is neat! so /selinux/null is the same thing as /dev/null.
> When a task exec's a new task and the child does not have permission
> to an open fd the kernel will close the fd and open /selinux/null in
> it's place. In this case it's not the label on the actual inode that
> is a problem but it is instead the label on the fd. at some point
> ifconfig_t was passed an fd it couldn't use and the kernel replaced
> it with /selinux/null. ifconfig then leaked that fd onto
> wpa_supplicant.
>
> My guess is that the real bug is whatever tried to pass ifconfig an
> fd which it was not allowed to use. Then we work from there.....
>
> -Eric
>
>
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>
>
These are the ones to me that look backwards.
I have a hard time seeing how for ifconfig_t could leak a descriptor to
NetworkManager_t.
Searching through transition rules, I guess the following is possible.
ifconfig_t -> insmod_t -> initrc_t -> NetworkManager_t?
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next prev parent reply other threads:[~2011-07-20 12:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-19 21:46 What is /selinux/null? Martin Orr
2011-07-20 1:31 ` Eric Paris
2011-07-20 12:58 ` Daniel J Walsh [this message]
2011-08-20 16:55 ` Martin Orr
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