netdev - Re: [PATCH 5/5] net: Use netlink_ns_capable to verify the permisions of netlink messages

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Date:	Thu, 8 May 2014 14:32:35 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Stephen Hemminger <stephen@...workplumber.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	"Jorge Boncompte [DTI2]" <jorge@...2.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Simo Sorce <ssorce@...hat.com>,
	"security@...nel.org" <security@...nel.org>,
	Network Development <netdev@...r.kernel.org>,
	"Serge E. Hallyn" <serge@...lyn.com>
Subject: Re: [PATCH 5/5] net: Use netlink_ns_capable to verify the permisions
 of netlink messages

On Thu, May 8, 2014 at 2:29 PM, Stephen Hemminger
<stephen@...workplumber.org> wrote:
> On Wed, 7 May 2014 16:34:08 -0700
> Linus Torvalds <torvalds@...ux-foundation.org> wrote:
>
>> On Wed, May 7, 2014 at 4:01 PM, Andy Lutomirski <luto@...capital.net> wrote:
>> >
>> > I agree that it should, but it doesn't, and if these patches get
>> > backported, things will break.  OTOH, if the patches don't get
>> > backported, things may still break, and we have a possibly rather
>> > severe unfixed vulnerability.
>>
>> How did this *use* to work? It looks like it drops permissions after
>> the bind(), so the actual _IO_ must have always been done without
>> permissions, no?
>>
>> Is it just a bind-time permission check that is now failing, because
>> it uses the credentials associated with the socket open? If so, I'd
>> suggest unding just the ns-capable change for bind(), and make that
>> one always use the current process effective one.
>>
>> If you're a suid application, you're not doing "bind()" on random file
>> descriptors that were passed to you. It's really just read/write that
>> need to be careful.
>>
>>             Linus
>
> Quagga drops privileges at startup then selectively raises them.
> The code is doing raise caps in netlink code for bind and each sendto
> and recvmsg call.
>
> Ideally it should be able to not have to raise/lower on each send/recvmsg
> call.
>

Why doesn't it just raise them and keep them raised?

--Andy
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