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Date:   Fri, 19 Nov 2021 14:43:59 -0800
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
Cc:     Andrey Konovalov <andreyknvl@gmail.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Chinwen Chang (=?UTF-8?Q?=E5=BC=B5=E9=8C=A6=E6=96=87?=) 
        <chinwen.chang@mediatek.com>,
        Nicholas Tang (=?UTF-8?Q?=E9=84=AD=E7=A7=A6?= =?UTF-8?Q?=E8=BC=9D?=) 
        <nicholas.tang@mediatek.com>,
        James Hsu ( =?UTF-8?Q?=E5=BE=90=E6=85=B6=E8=96=B0?=) 
        <James.Hsu@mediatek.com>,
        Yee Lee (=?UTF-8?Q?=E6=9D=8E=E5=BB=BA=E8=AA=BC?=) 
        <Yee.Lee@mediatek.com>, "linux-mm@kvack.org" <linux-mm@kvack.org>,
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        <linux-mediatek@lists.infradead.org>,
        kasan-dev <kasan-dev@googlegroups.com>,
        <kuan-ying.lee@mediatek.com>
Subject: Re: [PATCH] kmemleak: fix kmemleak false positive report with HW
 tag-based kasan enable
Message-Id: <20211119144359.b70d2fde7631bd14cd9652e3@linux-foundation.org>
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References: <20211118054426.4123-1-Kuan-Ying.Lee@mediatek.com>
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On Fri, 19 Nov 2021 23:12:55 +0800 Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> wrote:

> > > > Call sequence:
> > > > ptr = kmalloc(size, GFP_KERNEL);
> > > > page = virt_to_page(ptr);
> > > > kfree(page_address(page));
> > > > ptr = kmalloc(size, GFP_KERNEL);
> > 
> > How is this call sequence valid? page_address returns the address of
> > the start of the page, while kmalloced object could have been located
> > in the middle of it.
> 
> Thanks for pointing out. I miss the offset.
> 
> It should be listed as below.
> 
> ptr = kmalloc(size, GFP_KERNEL);
> page = virt_to_page(ptr);
> offset = offset_in_page(ptr);
> kfree(page_address(page) + offset);
> ptr = kmalloc(size, GFP_KERNEL);

I updated the changelog to reflect this.