linux-kernel - Re: [PATCH v2 2/9] procfs: add proc_allow_access() to check if file's opener may access task

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Message-ID: <CALCETrXa1uAAOM7U_Jk1APHx1aJGdJJy4ggJ9C+sn++btXX2FA@mail.gmail.com>
Date:	Fri, 4 Oct 2013 16:08:06 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Djalal Harouni <tixxdz@...ndz.org>,
	Kees Cook <keescook@...omium.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	"Serge E. Hallyn" <serge.hallyn@...ntu.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	David Rientjes <rientjes@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	Djalal Harouni <tixxdz@...il.com>
Subject: Re: [PATCH v2 2/9] procfs: add proc_allow_access() to check if file's
 opener may access task

On Fri, Oct 4, 2013 at 3:59 PM, Andy Lutomirski <luto@...capital.net> wrote:
>
> I'd really like a solution where there are no read or write
> implementations in the entire kernel that check permissions.  Failing
> that, just getting it for procfs would be nice.  (uid_map, etc will
> probably need to be revoked on unshare for this to work.)

By "check permissions" I mean using anything but f_cred.

uid_map won't need any form of revoke, though -- the stuct file
already points at a particular target ns.  I wonder why the
CAP_SYS_ADMIN check is in map_write instead of open, though.

--Andy
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