linux-kernel - Re: [PATCH 00/18] introduce a new tool, valid access checker

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Message-ID: <CACT4Y+ZwvVG7aEiZWj-OmbxVdQyFj0ebXnakjeVnar-GQACBfg@mail.gmail.com>
Date:   Wed, 29 Nov 2017 10:27:00 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Joonsoo Kim <js1304@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Wengang Wang <wen.gang.wang@...cle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 00/18] introduce a new tool, valid access checker

On Tue, Nov 28, 2017 at 8:48 AM,  <js1304@...il.com> wrote:
> From: Joonsoo Kim <iamjoonsoo.kim@....com>
>
> Hello,
>
> This patchset introduces a new tool, valid access checker.
>
> Vchecker is a dynamic memory error detector. It provides a new debug feature
> that can find out an un-intended access to valid area. Valid area here means
> the memory which is allocated and allowed to be accessed by memory owner and
> un-intended access means the read/write that is initiated by non-owner.
> Usual problem of this class is memory overwritten.
>
> Most of debug feature focused on finding out un-intended access to
> in-valid area, for example, out-of-bound access and use-after-free, and,
> there are many good tools for it. But, as far as I know, there is no good tool
> to find out un-intended access to valid area. This kind of problem is really
> hard to solve so this tool would be very useful.
>
> This tool doesn't automatically catch a problem. Manual runtime configuration
> to specify the target object is required.
>
> Note that there was a similar attempt for the debugging overwritten problem
> however it requires manual code modifying and recompile.
>
> http://lkml.kernel.org/r/<20171117223043.7277-1-wen.gang.wang@...cle.com>
>
> To get more information about vchecker, please see a documention at
> the last patch.
>
> Patchset can also be available at
>
> https://github.com/JoonsooKim/linux/tree/vchecker-master-v1.0-next-20171122
>
> Enjoy it.


Hi Joonsoo,

I skimmed through the code and this looks fine from KASAN point of
view (minimal code changes and no perf impact).
I don't feel like I can judge if this should go in or not. I will not
use this, we use KASAN for large-scale testing, but vchecker is in a
different bucket, it is meant for developers debugging hard bugs.
Wengang come up with a very similar change, and Andi said that this
looks useful.

If the decision is that this goes in, please let me take a closer look
before this is merged.

Thanks