linux-kernel - Re: [syzbot] KASAN: use-after-free Read in copy_page_from_iter

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Message-ID: <20220615132147.GA18252@lst.de>
Date:   Wed, 15 Jun 2022 15:21:47 +0200
From:   Christoph Hellwig <hch@....de>
To:     Qu Wenruo <quwenruo.btrfs@....com>
Cc:     Christoph Hellwig <hch@....de>, dsterba@...e.cz,
        syzbot <syzbot+d2dd123304b4ae59f1bd@...kaller.appspotmail.com>,
        akpm@...ux-foundation.org, clm@...com, dsterba@...e.com,
        josef@...icpanda.com, linux-btrfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, syzkaller-bugs@...glegroups.com,
        willy@...radead.org
Subject: Re: [syzbot] KASAN: use-after-free Read in
 copy_page_from_iter_atomic (2)

On Tue, Jun 14, 2022 at 04:50:22PM +0800, Qu Wenruo wrote:
> The same way as data?
>
> map-logical to find the location of a mirror, write 4 bytes of zero into
> the location, then call it a day.
>
> Although for metadata, you may want to choose a metadata that would
> definitely get read.
> Thus tree root is a good candidate.

And how do I find out the logic address of the tree root?