linux-kernel - Re: [PATCH RFC 1/2] mm: Extract SLAB

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Date:   Mon, 17 Aug 2020 13:53:51 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Kees Cook <keescook@...omium.org>,
        Alexander Popov <alex.popov@...ux.com>
Cc:     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>,
        Eric Biederman <ebiederm@...ssion.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Laura Abbott <labbott@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux Memory Management List <linux-mm@...ck.org>,
        kernel-hardening@...ts.openwall.com,
        LKML <linux-kernel@...r.kernel.org>, notify@...nel.org
Subject: Re: [PATCH RFC 1/2] mm: Extract SLAB_QUARANTINE from KASAN

On Sat, Aug 15, 2020 at 6:52 PM Kees Cook <keescook@...omium.org> wrote:
>
> On Thu, Aug 13, 2020 at 06:19:21PM +0300, Alexander Popov wrote:
> > Heap spraying is an exploitation technique that aims to put controlled
> > bytes at a predetermined memory location on the heap. Heap spraying for
> > exploiting use-after-free in the Linux kernel relies on the fact that on
> > kmalloc(), the slab allocator returns the address of the memory that was
> > recently freed. Allocating a kernel object with the same size and
> > controlled contents allows overwriting the vulnerable freed object.
> >
> > Let's extract slab freelist quarantine from KASAN functionality and
> > call it CONFIG_SLAB_QUARANTINE. This feature breaks widespread heap
> > spraying technique used for exploiting use-after-free vulnerabilities
> > in the kernel code.
> >
> > If this feature is enabled, freed allocations are stored in the quarantine
> > and can't be instantly reallocated and overwritten by the exploit
> > performing heap spraying.

[...]

> In doing this extraction, I wonder if function naming should be changed?
> If it's going to live a new life outside of KASAN proper, maybe call
> these functions quarantine_cache_*()? But perhaps that's too much
> churn...

If quarantine is to be used without the rest of KASAN, I'd prefer for
it to be separated from KASAN completely: move to e.g. mm/quarantine.c
and don't mention KASAN in function/config names.