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To:     Clay Harris <bugs@claycon.org>
Cc:     Jens Axboe <axboe@kernel.dk>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Jann Horn <jannh@google.com>, io-uring@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
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From:   Pavel Begunkov <asml.silence@gmail.com>
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Subject: Re: [PATCH for-5.7] splice: move f_mode checks to do_{splice,tee}()
Message-ID: <c202b074-1cb8-8bf0-3d42-c6c5dd68f2ee@gmail.com>
Date:   Wed, 6 May 2020 01:13:50 +0300
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On 06/05/2020 01:00, Clay Harris wrote:
> On Wed, May 06 2020 at 00:38:05 +0300, Pavel Begunkov quoth thus:
> 
>> On 06/05/2020 00:10, Clay Harris wrote:
>>> On Mon, May 04 2020 at 22:39:35 +0300, Pavel Begunkov quoth thus:
>>>
>>>> do_splice() is used by io_uring, as will be do_tee(). Move f_mode
>>>> checks from sys_{splice,tee}() to do_{splice,tee}(), so they're
>>>> enforced for io_uring as well.
>>>
>>> I'm not seeing any check against splicing a pipe to itself in the
>>> io_uring path, although maybe I just missed it.  As the comment
>>> below says: /* Splicing to self would be fun, but... */ .
>>
>> io_uring just forwards a request to do_splice(), which do the check at the exact
>> place you mentioned. The similar story is with do_tee().
> 
> Okay.  I'd been thinking that since you were moving the file mode
> checks into io_uring that the previous place they were called wasn't
> on the path.  Evidently, you're just moving the mode checks earlier.

I move them from sys_splice() later to do_splice(). Even though the patch
doesn't touch io_uring directly, it fixes a problem in there. And as a nice
addition, it looks prettier and removes a couple of useless checks.


-- 
Pavel Begunkov