linux-kernel - Re: [PATCH v4] kasan: add memory corruption identification for software tag-based mode

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Date:   Thu, 22 Aug 2019 09:22:02 +0800
From:   Walter Wu <walter-zh.wu@...iatek.com>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>
CC:     Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "Andrew Morton" <akpm@...ux-foundation.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Miles Chen <miles.chen@...iatek.com>,
        <linux-kernel@...r.kernel.org>, <kasan-dev@...glegroups.com>,
        <linux-mm@...ck.org>, <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>, <wsd_upstream@...iatek.com>
Subject: Re: [PATCH v4] kasan: add memory corruption identification for
 software tag-based mode

On Wed, 2019-08-21 at 20:52 +0300, Andrey Ryabinin wrote:
> 
> On 8/20/19 8:37 AM, Walter Wu wrote:
> > On Tue, 2019-08-06 at 13:43 +0800, Walter Wu wrote:
> >> This patch adds memory corruption identification at bug report for
> >> software tag-based mode, the report show whether it is "use-after-free"
> >> or "out-of-bound" error instead of "invalid-access" error. This will make
> >> it easier for programmers to see the memory corruption problem.
> >>
> >> We extend the slab to store five old free pointer tag and free backtrace,
> >> we can check if the tagged address is in the slab record and make a
> >> good guess if the object is more like "use-after-free" or "out-of-bound".
> >> therefore every slab memory corruption can be identified whether it's
> >> "use-after-free" or "out-of-bound".
> >>
> >> ====== Changes
> >> Change since v1:
> >> - add feature option CONFIG_KASAN_SW_TAGS_IDENTIFY.
> >> - change QUARANTINE_FRACTION to reduce quarantine size.
> >> - change the qlist order in order to find the newest object in quarantine
> >> - reduce the number of calling kmalloc() from 2 to 1 time.
> >> - remove global variable to use argument to pass it.
> >> - correct the amount of qobject cache->size into the byes of qlist_head.
> >> - only use kasan_cache_shrink() to shink memory.
> >>
> >> Change since v2:
> >> - remove the shinking memory function kasan_cache_shrink()
> >> - modify the description of the CONFIG_KASAN_SW_TAGS_IDENTIFY
> >> - optimize the quarantine_find_object() and qobject_free()
> >> - fix the duplicating function name 3 times in the header.
> >> - modify the function name set_track() to kasan_set_track()
> >>
> >> Change since v3:
> >> - change tag-based quarantine to extend slab to identify memory corruption
> > 
> > Hi,Andrey,
> > 
> > Would you review the patch,please?
> 
> 
> I didn't notice anything fundamentally wrong, but I find there are some
> questionable implementation choices that makes code look weirder than necessary
> and harder to understand. So I ended up with cleaning it up, see the diff bellow.
> I'll send v5 with that diff folded.
> 

Thanks your review and suggestion.

Walter