From: Kees Cook <kees@outflux.net>
To: Wolfram Gloger <wg@malloc.de>
Cc: dvyukov@google.com, ak@linux.intel.com,
linux-kernel@vger.kernel.org, pjt@google.com,
andreyknvl@google.com, kcc@google.com, x86@kernel.org
Subject: Re: Out-of-bounds access in get_wchan (arch/x86/kernel/process_64.c)
Date: Sat, 28 Sep 2013 14:01:11 -0700 [thread overview]
Message-ID: <20130928210111.GZ21253@outflux.net> (raw)
In-Reply-To: <u4zjqwg1xp.fsf@mail.malloc.de>
On Sat, Sep 28, 2013 at 09:51:14PM +0200, Wolfram Gloger wrote:
> Kees Cook <kees@outflux.net> writes:
>
> > Please note that these bounds checks aren't correct to begin with. Since
> > a pointer is being dereferenced, the end boundry must be reduced by
> > sizeof(unsigned long) as well.
> >
> > It looks like process_32.c suffers the same problems, too.
>
> I can't see the end boundary problem in process_32.c. The end checks
> are properly reduced with the top_esp and top_ebp macros.
>
> All I can see in process_32.c is that the check
>
> if (bp < stack_page || bp > top_ebp+stack_page)
>
> could be replaced by:
>
> if (bp < stack_page-sizeof(unsigned long) || bp > top_ebp+stack_page)
>
> but that is a relaxation and not an over/underrun fix.
>
> Can you elaborate what problem you see in process_32.c?
Ah, yes, sorry, this appears to only be a problem in process_64.c. I didn't look
closely enough. I see now that top_esp and top_ebp correctly reduce the size of
THREAD_SIZE. Thanks!
-Kees
--
Kees Cook @outflux.net
prev parent reply other threads:[~2013-09-28 21:01 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-03 14:41 Out-of-bounds access in get_wchan (arch/x86/kernel/process_64.c) Dmitry Vyukov
2013-09-10 22:06 ` Andi Kleen
2013-09-11 18:16 ` Dmitry Vyukov
2013-09-27 19:03 ` Kees Cook
2013-09-28 19:51 ` Wolfram Gloger
2013-09-28 21:01 ` Kees Cook [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130928210111.GZ21253@outflux.net \
--to=kees@outflux.net \
--cc=ak@linux.intel.com \
--cc=andreyknvl@google.com \
--cc=dvyukov@google.com \
--cc=kcc@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=pjt@google.com \
--cc=wg@malloc.de \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).