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Subject: Re: [PATCH v3 0/2] iter revert problems
To:     Pavel Begunkov <asml.silence@gmail.com>, io-uring@vger.kernel.org,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>
Cc:     Palash Oswal <oswalpalash@gmail.com>,
        Sudip Mukherjee <sudipm.mukherjee@gmail.com>,
        linux-kernel@vger.kernel.org,
        syzbot+9671693590ef5aad8953@syzkaller.appspotmail.com
References: <cover.1629713020.git.asml.silence@gmail.com>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <65d27d2d-30f1-ccca-1755-fcf2add63c44@kernel.dk>
Date:   Fri, 3 Sep 2021 14:55:26 -0600
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On 8/23/21 4:18 AM, Pavel Begunkov wrote:
> iov_iter_revert() doesn't go well with iov_iter_truncate() in all
> cases, see 2/2 for the bug description. As mentioned there the current
> problems is because of generic_write_checks(), but there was also a
> similar case fixed in 5.12, which should have been triggerable by normal
> write(2)/read(2) and others.
> 
> It may be better to enforce reexpands as a long term solution, but for
> now this patchset is quickier and easier to backport.
> 
> v2: don't fail if it was justly fully reverted
> v3: use truncated size + reexapand based approach

Al, let's get this upstream. How do you want to handle it? I can take
it through the io_uring tree, or it can go through your tree. I really
don't care which route it takes, but we should get this upstream as
it solves a real problem.

-- 
Jens Axboe