From: Kees Cook <keescook@chromium.org>
To: David Rientjes <rientjes@google.com>
Cc: linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Minchan Kim <minchan@kernel.org>, Joe Perches <joe@perches.com>,
Kautuk Consul <consul.kautuk@gmail.com>,
linux-mm@kvack.org, Brad Spengler <spender@grsecurity.net>
Subject: Re: [PATCH] mm: use %pK for /proc/vmallocinfo
Date: Wed, 3 Oct 2012 11:39:27 -0700 [thread overview]
Message-ID: <CAGXu5jKAYYd5MxF4QmUxuFtAx2V8j3GMtmcA5v6ShGHAQZQh7Q@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1210031051150.29765@chino.kir.corp.google.com>
On Wed, Oct 3, 2012 at 11:02 AM, David Rientjes <rientjes@google.com> wrote:
> On Wed, 3 Oct 2012, Kees Cook wrote:
>
>> > So root does echo 0 > /proc/sys/kernel/kptr_restrict first. Again: what
>> > are you trying to protect?
>>
>> Only CAP_SYS_ADMIN can change the setting. This is, for example, for
>> containers, or other situations where a uid 0 process lacking
>> CAP_SYS_ADMIN cannot see virtual addresses. It's a very paranoid case,
>> yes, but it's part of how this feature was designed. Think of it as
>> supporting the recent uid 0 vs ring 0 boundary. :)
>>
>
> The intention of /proc/vmallocinfo being S_IRUSR is obviously to only
> allow root to read this information to begin with, so if root lacks
> CAP_SYS_ADMIN then it seems the best fix would be to return an empty file
> on read()? Or give permission to everybody to read it but only return a
> positive count when they have CAP_SYS_ADMIN?
>
> There's no need to make this so convoluted that you need to have the right
> combination of uid, kptr_restrict, CAP_SYS_ADMIN, and CAP_SYSLOG to get
> anything valuable out of this file, though.
Well, the existing mechanism is using %pK. I see no reason to add
additional complexity.
-Kees
--
Kees Cook
Chrome OS Security
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prev parent reply other threads:[~2012-10-03 18:39 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-02 23:49 Kees Cook
2012-10-03 0:43 ` KOSAKI Motohiro
2012-10-03 5:12 ` David Rientjes
2012-10-03 5:15 ` Kees Cook
2012-10-03 5:37 ` David Rientjes
2012-10-03 16:13 ` Kees Cook
2012-10-03 18:02 ` David Rientjes
2012-10-03 18:39 ` Kees Cook [this message]
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