From: Kees Cook <kees@outflux.net>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Andi Kleen <ak@linux.intel.com>, Wolfram Gloger <wg@malloc.de>,
LKML <linux-kernel@vger.kernel.org>, Paul Turner <pjt@google.com>,
Andrey Konovalov <andreyknvl@google.com>,
Kostya Serebryany <kcc@google.com>,
x86@kernel.org
Subject: Re: Out-of-bounds access in get_wchan (arch/x86/kernel/process_64.c)
Date: Fri, 27 Sep 2013 12:03:12 -0700 [thread overview]
Message-ID: <20130927190312.GV21253@outflux.net> (raw)
In-Reply-To: <CACT4Y+Y2-d0TFq=oq-xFt8udrYc0r8_aROdUfVU29KJBhwWpAQ@mail.gmail.com>
On Wed, Sep 11, 2013 at 10:16:32PM +0400, Dmitry Vyukov wrote:
> On Wed, Sep 11, 2013 at 2:06 AM, Andi Kleen <ak@linux.intel.com> wrote:
> >> Indeed, get_wchan ensures that fp<stack+THREAD_SIZE, but then dereferences fp+8:
> >>
> >> 434 if (fp < (unsigned long)stack ||
> >> 435 fp >= (unsigned long)stack+THREAD_SIZE)
> >> 436 return 0;
> >> 437 ip = *(u64 *)(fp+8);
> >>
> >> It must check that fp+8<stack+THREAD_SIZE.
> >> As far as I see, the bug can lead to garbage return values or in the
> >> worst case to crash.
> >
> > Thanks for the report.
> >
> > The change looks good to me. Can you please submit a formal signed off patch
> > to x86@kernel.org ?
Can you CC this to lkml as well? x86@ isn't a public list, IIUC.
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.
-Kees
--
Kees Cook @outflux.net
next prev parent reply other threads:[~2013-09-27 19:03 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 [this message]
2013-09-28 19:51 ` Wolfram Gloger
2013-09-28 21:01 ` Kees Cook
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