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From: Wolfram Gloger <wg@malloc.de>
To: Kees Cook <kees@outflux.net>
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 21:51:14 +0200	[thread overview]
Message-ID: <u4zjqwg1xp.fsf@mail.malloc.de> (raw)
In-Reply-To: <20130927190312.GV21253@outflux.net> (message from Kees Cook on Fri, 27 Sep 2013 12:03:12 -0700)

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?

Regards,
Wolfram.

  reply	other threads:[~2013-09-28 19:51 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-09-03 14:41 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 [this message]
2013-09-28 21:01         ` Kees Cook

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