linux-kernel - Re: [PATCH v2 1/2] mm, kasan: don't call kasan

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Message-ID: <CAG_fn=XTeQ5TgxWRKSnAt3b+rkw4H6c=h3h36UGMeBben4TMsA@mail.gmail.com>
Date:	Thu, 28 Apr 2016 13:31:14 +0200
From:	Alexander Potapenko <glider@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andrey Konovalov <adech.fo@...il.com>,
	Dmitriy Vyukov <dvyukov@...gle.com>,
	Christoph Lameter <cl@...ux.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Kostya Serebryany <kcc@...gle.com>,
	kasan-dev <kasan-dev@...glegroups.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [PATCH v2 1/2] mm, kasan: don't call kasan_krealloc() from ksize().

On Fri, Apr 22, 2016 at 11:32 PM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Wed, 13 Apr 2016 13:20:09 +0200 Alexander Potapenko <glider@...gle.com> wrote:
>
>> Instead of calling kasan_krealloc(), which replaces the memory allocation
>> stack ID (if stack depot is used), just unpoison the whole memory chunk.
>
> I don't understand why these two patches exist.  Bugfix?  Cleanup?
> Optimization?
It's incorrect to call kasan_krealloc() from ksize(), because the
former may touch the allocation metadata (it does so for the SLAB
allocator).
Yes, this is a bugfix.
>
> I had to change kmalloc_tests_init() a bit due to
> mm-kasan-initial-memory-quarantine-implementation.patch:
>
>         kasan_stack_oob();
>         kasan_global_oob();
>  #ifdef CONFIG_SLAB
>         kasan_quarantine_cache();
>  #endif
> +       ksize_unpoisons_memory();
>         return -EAGAIN;
>  }
>
> Please check.
Ack.



-- 
Alexander Potapenko
Software Engineer

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