Re: [PATCH 1/2] splice: export do_tee()

From: Pavel Begunkov <asml.silence@gmail.com>
To: Jens Axboe <axboe@kernel.dk>, Jann Horn <jannh@google.com>
Cc: io-uring <io-uring@vger.kernel.org>,
	kernel list <linux-kernel@vger.kernel.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Clay Harris <bugs@claycon.org>
Subject: Re: [PATCH 1/2] splice: export do_tee()
Date: Mon, 4 May 2020 19:36:25 +0300	[thread overview]
Message-ID: <9d43b5b5-577b-bc44-1667-fdd2055e63d7@gmail.com> (raw)
In-Reply-To: <1007c4ff-2af0-1473-a268-a0ae245d8188@gmail.com>

On 04/05/2020 17:03, Pavel Begunkov wrote:
> On 04/05/2020 16:43, Jens Axboe wrote:
>> On 5/4/20 6:31 AM, Pavel Begunkov wrote:
>>> On 04/05/2020 14:09, Jann Horn wrote:
>>>> On Sat, May 2, 2020 at 2:10 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
>>>>> export do_tee() for use in io_uring
>>>> [...]
>>>>> diff --git a/fs/splice.c b/fs/splice.c
>>>> [...]
>>>>>   * The 'flags' used are the SPLICE_F_* variants, currently the only
>>>>>   * applicable one is SPLICE_F_NONBLOCK.
>>>>>   */
>>>>> -static long do_tee(struct file *in, struct file *out, size_t len,
>>>>> -                  unsigned int flags)
>>>>> +long do_tee(struct file *in, struct file *out, size_t len, unsigned int flags)
>>>>>  {
>>>>>         struct pipe_inode_info *ipipe = get_pipe_info(in);
>>>>>         struct pipe_inode_info *opipe = get_pipe_info(out);
>>>>
>>>> AFAICS do_tee() in its current form is not something you should be
>>>> making available to anything else, because the file mode checks are
>>>> performed in sys_tee() instead of in do_tee(). (And I don't see any
>>>> check for file modes in your uring patch, but maybe I missed it?) If
>>>> you want to make do_tee() available elsewhere, please refactor the
>>>> file mode checks over into do_tee().
>>>
>>> Overlooked it indeed. Glad you found it
>>
>> Yeah indeed, that's a glaring oversight on my part too. Will you send
>> a patch for 5.7-rc as well for splice?
> 
> Absolutely

The right way would be to do as Jann proposed, but would you prefer an
io_uring.c local fix for-5.7 and then a proper one? I assume it could be easier
to manage.

-- 
Pavel Begunkov