Re: [PATCH RFC 1/2] mm: Extract SLAB_QUARANTINE from KASAN

[Andrey Konovalov <andreyknvl@google.com>]

On Sat, Aug 15, 2020 at 6:52 PM Kees Cook <keescook@chromium.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.