linux-kernel - Re: [PATCH RFC 2/2] lkdtm: Add heap spraying test

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Date:   Mon, 17 Aug 2020 12:24:29 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Alexander Popov <alex.popov@...ux.com>,
        Jann Horn <jannh@...gle.com>, Will Deacon <will@...nel.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Patrick Bellasi <patrick.bellasi@....com>,
        David Howells <dhowells@...hat.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Laura Abbott <labbott@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org,
        notify@...nel.org, Kexec Mailing List <kexec@...ts.infradead.org>
Subject: Re: [PATCH RFC 2/2] lkdtm: Add heap spraying test

On Mon, Aug 17, 2020 at 01:24:37PM -0500, Eric W. Biederman wrote:
> Alexander Popov <alex.popov@...ux.com> writes:
> 
> > Add a simple test for CONFIG_SLAB_QUARANTINE.
> >
> > It performs heap spraying that aims to reallocate the recently freed heap
> > object. This technique is used for exploiting use-after-free
> > vulnerabilities in the kernel code.
> >
> > This test shows that CONFIG_SLAB_QUARANTINE breaks heap spraying
> > exploitation technique.
> >
> > Signed-off-by: Alexander Popov <alex.popov@...ux.com>
> 
> Why put this test in the linux kernel dump test module?
> 
> I have no problem with tests, and I may be wrong but this
> does not look like you are testing to see if heap corruption
> triggers a crash dump.  Which is what the rest of the tests
> in lkdtm are about.  Seeing if the test triggers successfully
> triggers a crash dump.

The scope of LKDTM has shifted a bit, and I'm fine with tests that
don't cause crashes as long as they're part of testing system-wide
defenses, etc. It's easier to collect similar tests together (even if
they don't break the system).

-- 
Kees Cook