linux-kernel - Re: [PATCH 2/2] kasan: add test for invalid size in memmove

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Date:   Mon, 14 Oct 2019 23:57:11 +0800
From:   Walter Wu <walter-zh.wu@...iatek.com>
To:     Matthew Wilcox <willy@...radead.org>
CC:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <kasan-dev@...glegroups.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>, <wsd_upstream@...iatek.com>
Subject: Re: [PATCH 2/2] kasan: add test for invalid size in memmove

On Mon, 2019-10-14 at 08:07 -0700, Matthew Wilcox wrote:
> On Mon, Oct 14, 2019 at 06:36:54PM +0800, Walter Wu wrote:
> > Test size is negative numbers in memmove in order to verify
> > whether it correctly get KASAN report.
> 
> You're not testing negative numbers, though.  memmove() takes an unsigned
> type, so you're testing a very large number.
> 
Casting negative numbers to size_t would indeed turn up as a "large"
size_t and its value will be larger than ULONG_MAX/2. We mainly want to
express this case. Maybe we can add some descriptions. Thanks for your
reminder.