linux-kernel - Re: [PATCH v3 1/2] kasan: catch invalid free before SLUB reinitializes the object

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Message-ID: <CAG48ez17_Etm_-AMaJHENq=QjtCRqNcCe9VUDvNw8En49wKybg@mail.gmail.com>
Date: Tue, 30 Jul 2024 12:30:34 +0200
From: Jann Horn <jannh@...gle.com>
To: Andrey Konovalov <andreyknvl@...il.com>
Cc: Andrey Ryabinin <ryabinin.a.a@...il.com>, Alexander Potapenko <glider@...gle.com>, 
	Dmitry Vyukov <dvyukov@...gle.com>, Vincenzo Frascino <vincenzo.frascino@....com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Christoph Lameter <cl@...ux.com>, 
	Pekka Enberg <penberg@...nel.org>, David Rientjes <rientjes@...gle.com>, 
	Joonsoo Kim <iamjoonsoo.kim@....com>, Vlastimil Babka <vbabka@...e.cz>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Hyeonggon Yoo <42.hyeyoo@...il.com>, 
	Marco Elver <elver@...gle.com>, kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org
Subject: Re: [PATCH v3 1/2] kasan: catch invalid free before SLUB
 reinitializes the object

On Sat, Jul 27, 2024 at 2:47 AM Andrey Konovalov <andreyknvl@...il.com> wrote:
> On Fri, Jul 26, 2024 at 3:52 PM Jann Horn <jannh@...gle.com> wrote:
> >
> > > Do we still need this patch?
> >
> > I just tried removing this patch from the series; without it, the
> > kmem_cache_invalid_free kunit test fails because the kmem_cache_free()
> > no longer synchronously notices that the pointer is misaligned. I
> > guess I could change the testcase like this to make the tests pass
> > without this patch, but I'd like to hear from you or another KASAN
> > person whether you think that's a reasonable change:
>
> Ah, I see. I think detecting a bug earlier if we can is better. So I
> don't mind keeping this patch, was just confused by the commit
> message.

ack, changed it in v4

> Adding on top of my comments from before: I think if you move
> check_slab_free() out of poison_slab_object() (but add to
> __kasan_mempool_poison_object()), and move is_kfence_address() and
> kasan_arch_is_ready() to poison_slab_object()'s callers, you won't
> even need the free_validation_result enum, so the patch should become
> simpler.

right, makes sense, changed in v4

> You can also rename check_slab_free() to check_slab_allocation() to
> make it be named similarly to the already existing
> check_page_allocation().

done in v4