linux-kernel - Re: [PATCH v5 1/2] mm, kasan: improve double-free detection

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Message-ID: <5759A0A9.3080301@virtuozzo.com>
Date:	Thu, 9 Jun 2016 20:00:25 +0300
From:	Andrey Ryabinin <aryabinin@...tuozzo.com>
To:	Kuthonuzo Luruo <kuthonuzo.luruo@....com>, <glider@...gle.com>,
	<dvyukov@...gle.com>, <cl@...ux.com>, <penberg@...nel.org>,
	<rientjes@...gle.com>, <iamjoonsoo.kim@....com>,
	<akpm@...ux-foundation.org>
CC:	<kasan-dev@...glegroups.com>, <linux-kernel@...r.kernel.org>,
	<ynorov@...iumnetworks.com>
Subject: Re: [PATCH v5 1/2] mm, kasan: improve double-free detection

On 06/07/2016 09:03 PM, Kuthonuzo Luruo wrote:

Next time, when/if you send patch series, send patches in one thread, i.e. patches should be replies to the cover letter.
Your patches are not linked together, which makes them harder to track.


> Currently, KASAN may fail to detect concurrent deallocations of the same
> object due to a race in kasan_slab_free(). This patch makes double-free
> detection more reliable by serializing access to KASAN object metadata.
> New functions kasan_meta_lock() and kasan_meta_unlock() are provided to
> lock/unlock per-object metadata. Double-free errors are now reported via
> kasan_report().
> 
> Per-object lock concept from suggestion/observations by Dmitry Vyukov.
> 


So, I still don't like this, this too way hacky and complex.
I have some thoughts about how to make this lockless and robust enough.
I'll try to sort this out tomorrow.