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

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Message-ID: <CA+55aFzZg3LfpPpx3+83sB0npd9863NTMqvsCArMDjg-9J151A@mail.gmail.com>
Date:	Wed, 7 May 2014 16:34:08 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	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 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
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