netdev - Re: [RFC][PATCH] netlink: Only check file credentials for implicit destinations

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Date:	Mon, 26 May 2014 15:39:07 +0200
From:	Willy Tarreau <w@....eu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andy Lutomirski <luto@...capital.net>,
	"Jorge Boncompte [DTI2]" <jorge@...2.net>,
	Jiri Benc <jbenc@...hat.com>,
	David Miller <davem@...emloft.net>,
	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>,
	Michael Kerrisk-manpages <mtk.manpages@...il.com>
Subject: Re: [RFC][PATCH] netlink: Only check file credentials for implicit destinations

On Sun, May 25, 2014 at 05:32:55PM -0700, Linus Torvalds wrote:
> On Sun, May 25, 2014 at 4:44 PM, Eric W. Biederman
> <ebiederm@...ssion.com> wrote:
> >
> > But I agree that since connect on sockets is really the equivalent of
> > open on files, and unprivileged users can change where a socket is
> > connected to, using a struct cred captured at connect() time is better
> > than the struct cred captured at socket() time.
> 
> Ack. Conceptually, "connect/listen" really ends up being the
> equivalent to pathname lookup, not so much "socket()", which just
> mostly creates the placeholder for future work.
> 
> That would also be very much consistent with making "sendto" look at
> current creds rather than cached creds (but only _if_ it has an
> address, of course - using "sendto(... , NULL, 0)" should _not_
> somehow be different from "send()"). So I think that from a
> sensibility and "please explain the semantics to me" standpoint, that
> would be sane semantics.

I like this! And it's very much consistent with sendto() being used
as an alternative to connect() with TCP Fastopen.

Willy

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