linux-kernel - Re: [PATCH v2] vfs: Tighten up linkat(..., AT_EMPTY

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Message-ID: <CA+55aFw3AM2Xe2aNUKk0x8ZrZHbY4QnaRZbZdAqf1trT+dGDmQ@mail.gmail.com>
Date:	Thu, 22 Aug 2013 12:23:58 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Willy Tarreau <w@....eu>,
	"security@...nel.org" <security@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	Brad Spengler <spender@...ecurity.net>
Subject: Re: [PATCH v2] vfs: Tighten up linkat(..., AT_EMPTY_PATH)

On Thu, Aug 22, 2013 at 12:05 PM, Andy Lutomirski <luto@...capital.net> wrote:
>
> Does this work for the procfs case?  As far as I understand it (which
> isn't saying much), it goes through the symlink-following path.

Right. The /proc case is still separate, and we really should do
something about that too. But again, I don't think I_LINKABLE is the
thing to use there either. We probably should tighten up the magic
/proc follow-link a lot.

> What if we added another field to struct nameidata that's indicates
> what restrictions need to be enforced when following magical symlinks
> and then enforcing them when nd_jump_link gets used.  (There are only
> two of these, both in procfs.)

Yes, I think that might be just the kind of thing to do. Except some
tightening could well be quite regardless of any extra flags.

            Linus
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