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Date: Sun, 16 Aug 2020 21:59:30 +0200
From: Pavel Machek <pavel@...x.de>
To: Matthew Wilcox <willy@...radead.org>
Cc: Alexander Popov <alex.popov@...ux.com>,
Kees Cook <keescook@...omium.org>, 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@...glegroups.com, linux-mm@...ck.org,
kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org,
notify@...nel.org
Subject: Re: [PATCH RFC 1/2] mm: Extract SLAB_QUARANTINE from KASAN
On Sat 2020-08-15 19:54:55, Matthew Wilcox wrote:
> On Thu, Aug 13, 2020 at 06:19:21PM +0300, Alexander Popov wrote:
> > +config SLAB_QUARANTINE
> > + bool "Enable slab freelist quarantine"
> > + depends on !KASAN && (SLAB || SLUB)
> > + help
> > + Enable slab freelist quarantine to break 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.
> > + This feature is a part of KASAN functionality.
>
> After this patch, it isn't part of KASAN any more ;-)
>
> The way this is written is a bit too low level. Let's write it in terms
> that people who don't know the guts of the slab allocator or security
> terminology can understand:
>
> Delay reuse of freed slab objects. This makes some security
> exploits harder to execute. It reduces performance slightly
> as objects will be cache cold by the time they are reallocated,
> and it costs a small amount of memory.
Written this way, it invites questions:
Does it introduce any new deadlocks in near out-of-memory situations?
Best regards,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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