linux-kernel - Re: [PATCH resend - v2 0/2] procfs: make /proc/*/{stack,syscall,pagemap} 0400

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Date:	Sat, 22 Mar 2014 08:23:26 -0600
From:	Kees Cook <keescook@...omium.org>
To:	Djalal Harouni <tixxdz@...ndz.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andy Lutomirski <luto@...capital.net>,
	Oleg Nesterov <oleg@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH resend - v2 0/2] procfs: make /proc/*/{stack,syscall,pagemap}
 0400

On Sat, Mar 22, 2014 at 7:37 AM, Djalal Harouni <tixxdz@...ndz.org> wrote:
> (Please note: this is a resend of version 2, I got two Acked-by, but no
> one replied on why it should not be applied...)
>
>
> The following patches make /proc/*/{stack,syscall,personality,pagemap}
> 0400.
>
> These files contain sensitive information that can be used by an
> unprivileged process to leak address space and bypass ASLR. This will
> make the VFS able to bloc unprivileged processes from getting file
> descriptors on *already* *running* processes (privileged processes).
>
> This does not protect all the /proc and exec-suid cases. It just reduces
> the scope of ASLR leaks by protecting *already running* processes. The
> leak is still possible on these files *only* if an attacker opens its
> /proc/*/file and can *spawn* a target setuid process, then read from it.
>
> So, only already running processes are protected.
>
> Patches were Acked by Kees Cook and Andy Lutomirski. Thank you!
>
>
> This is a resend, first send:
> https://lkml.org/lkml/2013/12/15/114
>
> Of the already version 2, the original discussion:
> https://lkml.org/lkml/2013/8/26/354
> (date: Aug 2013, and it can be used to leak ASLR).
>
>
> Kees Cook also confirmed the security exposure here:
> https://lkml.org/lkml/2013/8/28/564
>
> At least we have a VFS protection for now.

Yes please. :)

Thanks for resending this!

-Kees

>
>
> Reminder:
> I've discussed the technique to use the 'file->f_cred' to protect proc
> entries here:
> https://lkml.org/lkml/2013/10/1/371
>
> Eric suggest it, I did the implementation and it was rejected.
>
> Good I've took _all_ the comments in consideration, and came up with
> another scheme. It will protect *already running* processes, but first
> I need to get this simple series accepted!
>
>
> Thanks!
>
>
> Djalal Harouni (2):
>  procfs: make /proc/*/{stack,syscall,personality} 0400
>  procfs: make /proc/*/pagemap 0400
>
>  fs/proc/base.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)



-- 
Kees Cook
Chrome OS Security
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