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Date: Sun, 11 Mar 2012 18:01:25 +0100
From: Djalal Harouni <tixxdz@...ndz.org>
To: Alexey Dobriyan <adobriyan@...il.com>
Cc: linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com,
Andrew Morton <akpm@...ux-foundation.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Al Viro <viro@...iv.linux.org.uk>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Vasiliy Kulikov <segoon@...nwall.com>,
Kees Cook <keescook@...omium.org>,
Solar Designer <solar@...nwall.com>,
WANG Cong <xiyou.wangcong@...il.com>,
James Morris <james.l.morris@...cle.com>,
Oleg Nesterov <oleg@...hat.com>,
linux-security-module@...r.kernel.org,
linux-fsdevel@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>,
Greg KH <gregkh@...uxfoundation.org>, Ingo Molnar <mingo@...e.hu>,
Stephen Wilson <wilsons@...rt.ca>,
"Jason A. Donenfeld" <Jason@...c4.com>
Subject: Re: [PATCH 8/9] proc: protect /proc/<pid>/{environ,pagemap} across
execve
On Sun, Mar 11, 2012 at 11:05:23AM +0300, Alexey Dobriyan wrote:
> On Sun, Mar 11, 2012 at 12:25:18AM +0100, Djalal Harouni wrote:
> > The /proc/<pid>/{environ,pagemap} are sensitive files which must be
> > protected across execve to avoid information leaks.
> >
> > These files are protected by attaching them to their task at open time by
> > saving the exec_id of the target task, this way in read we just compare
> > the target task's exec_id and the previously saved exec_id of the
> > proc_file_private struct, in other words we just bind these files to their
> > appropriate process image at open time. We do this since we are able to do
> > proper permission checks (ptrace) at each syscall, so we do not care about
> > the reader.
> >
> > Another important rule is to set the exec_id of the target task before the
> > permission checks at open, this way we do not race against target task
> > execve, and it will be more effective if the exec_id check at read/write
> > times are delayed as much as possible to be sure that the target task do
> > not change during execve.
> >
> > This patch adds the open file_operation to the
> > /proc/<pid>/{environ,pagemap} so we are able to set the exec_id of the
> > target task and to do the appropriate permission checks. The exec_id check
> > is done in the related read file_operation.
>
> ->open is duplicated.
Right, I'll unify the code in a generic open function that does:
* alloc and setup proc_file_private (which includes the exec_id)
* ptrace check using mm_for_maps()
unify only those who check PTRACE_MODE_READ
* save priv_file_proc.
This applies also to the release functions, I'll re-submit it.
Thanks Alexey.
--
tixxdz
http://opendz.org
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