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Date: Tue, 6 Oct 2020 08:35:50 +0000 (UTC)
From: Christopher Lameter <>
To: Kees Cook <>
cc: Matthew Wilcox <>, Jann Horn <>, 
    Alexander Popov <>, Will Deacon <>, 
    Andrey Ryabinin <>, 
    Alexander Potapenko <>, 
    Dmitry Vyukov <>, Pekka Enberg <>, 
    David Rientjes <>, Joonsoo Kim <>, 
    Andrew Morton <>, 
    Masahiro Yamada <>, 
    Masami Hiramatsu <>, 
    Steven Rostedt <>, 
    Peter Zijlstra <>, 
    Krzysztof Kozlowski <>, 
    Patrick Bellasi <>, 
    David Howells <>, 
    Eric Biederman <>, 
    Johannes Weiner <>, Laura Abbott <>, 
    Arnd Bergmann <>, 
    Greg Kroah-Hartman <>, 
    Daniel Micay <>, 
    Andrey Konovalov <>, Pavel Machek <>, 
    Valentin Schneider <>, 
    kasan-dev <>, Linux-MM <>, 
    Kernel Hardening <>, 
    kernel list <>,
Subject: Re: [PATCH RFC v2 0/6] Break heap spraying needed for exploiting

On Mon, 5 Oct 2020, Kees Cook wrote:

> > 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 ...
> Isn't the "easy" version of this already controlled by slab_merge? (i.e.
> do not share same-sized/flagged kmem_caches between different caches)


> The large trouble are the kmalloc caches, which don't have types
> associated with them. Having implicit kmem caches based on the type
> being allocated there would need some pretty extensive plumbing, I
> think?

Actually typifying those accesses may get rid of a lot of kmalloc
allocations and could help to ease the management and control of objects.

It may be a big task though given the ubiquity of kmalloc and the need to
create a massive amount of new slab caches. This is going to reduce the
cache hit rate significantly.

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