linux-kernel - Re: [PATCH RFC v2 0/6] Break heap spraying needed for exploiting use-after-free

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Message-ID: <20201006004414.GP20115@casper.infradead.org>
Date:   Tue, 6 Oct 2020 01:44:14 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Jann Horn <jannh@...gle.com>
Cc:     Alexander Popov <alex.popov@...ux.com>,
        Kees Cook <keescook@...omium.org>,
        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>,
        Daniel Micay <danielmicay@...il.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Pavel Machek <pavel@...x.de>,
        Valentin Schneider <valentin.schneider@....com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux-MM <linux-mm@...ck.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        kernel list <linux-kernel@...r.kernel.org>, notify@...nel.org
Subject: Re: [PATCH RFC v2 0/6] Break heap spraying needed for exploiting
 use-after-free

On Tue, Oct 06, 2020 at 12:56:33AM +0200, Jann Horn wrote:
> It seems to me like, if you want to make UAF exploitation harder at
> the heap allocator layer, you could do somewhat more effective things
> with a probably much smaller performance budget. Things like
> preventing the reallocation of virtual kernel addresses with different
> types, such that an attacker can only replace a UAF object with
> another object of the same type. (That is not an idea I like very much
> either, but I would like it more than this proposal.) (E.g. some
> browsers implement things along those lines, I believe.)

The slab allocator already has that functionality.  We call it
TYPESAFE_BY_RCU, but if forcing that on by default would enhance security
by a measurable amount, it wouldn't be a terribly hard sell ...