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Subject: Re: [PATCH v3 0/2] iter revert problems
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     Pavel Begunkov <asml.silence@gmail.com>, io-uring@vger.kernel.org,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        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>
 <65d27d2d-30f1-ccca-1755-fcf2add63c44@kernel.dk>
 <YTKZwuUtJJDQb8F+@zeniv-ca.linux.org.uk>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <72e3c837-8e44-8bc3-36c2-4a8682892a62@kernel.dk>
Date:   Fri, 3 Sep 2021 18:57:30 -0600
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On 9/3/21 3:55 PM, Al Viro wrote:
> On Fri, Sep 03, 2021 at 02:55:26PM -0600, Jens Axboe wrote:
>> 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.
> 
> Grabbed, will test and send a pull request...

Thanks Al! We should mark these for stable as well.

-- 
Jens Axboe