linux-kernel - Re: [PATCH v3 0/2] iter revert problems

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Message-ID: <YTKZwuUtJJDQb8F+@zeniv-ca.linux.org.uk>
Date:   Fri, 3 Sep 2021 21:55:14 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Pavel Begunkov <asml.silence@...il.com>, io-uring@...r.kernel.org,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Palash Oswal <oswalpalash@...il.com>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        linux-kernel@...r.kernel.org,
        syzbot+9671693590ef5aad8953@...kaller.appspotmail.com
Subject: Re: [PATCH v3 0/2] iter revert problems

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...