From: Jens Axboe <axboe@kernel.dk>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Max Kellermann <mk@cm4all.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH] fs/io_uring: fix O_PATH fds in openat, openat2, statx
Date: Thu, 7 May 2020 20:28:10 -0600 [thread overview]
Message-ID: <629de3b6-cf80-fe37-1dde-7f0464da0a04@kernel.dk> (raw)
In-Reply-To: <20200507233132.GJ23230@ZenIV.linux.org.uk>
On 5/7/20 5:31 PM, Al Viro wrote:
> On Thu, May 07, 2020 at 05:03:17PM -0600, Jens Axboe wrote:
>> On 5/7/20 4:44 PM, Al Viro wrote:
>>> On Thu, May 07, 2020 at 04:25:24PM -0600, Jens Axboe wrote:
>>>
>>>> static int io_close(struct io_kiocb *req, bool force_nonblock)
>>>> {
>>>> + struct files_struct *files = current->files;
>>>> int ret;
>>>>
>>>> req->close.put_file = NULL;
>>>> - ret = __close_fd_get_file(req->close.fd, &req->close.put_file);
>>>> + spin_lock(&files->file_lock);
>>>> + if (req->file->f_op == &io_uring_fops ||
>>>> + req->close.fd == req->ctx->ring_fd) {
>>>> + spin_unlock(&files->file_lock);
>>>> + return -EBADF;
>>>> + }
>>>> +
>>>> + ret = __close_fd_get_file_locked(files, req->close.fd,
>>>> + &req->close.put_file);
>>>
>>> Pointless. By that point req->file might have nothing in common with
>>> anything in any descriptor table.
>>
>> How about the below then? Stop using req->file, defer the lookup until
>> we're in the handler instead. Not sure the 'fd' check makes sense
>> at this point, but at least we should be consistent in terms of
>> once we lookup the file and check the f_op.
>
> Actually, what _is_ the reason for that check? Note, BTW, that if the
> file in question happens to be an AF_UNIX socket, closing it will
> close all references held in SCM_RIGHTS datagrams sitting in its queue,
> which might very well include io_uring files.
>
> IOW, if tries to avoid something really unpleasant, it's not enough.
> And if it doesn't, then what is it for?
Maybe there is no issue at all, the point was obviously to not have
io_uring close itself. But we might just need an ordering of the
fput vs put_request to make that just fine. Let me experiment a bit
and see what's going on.
--
Jens Axboe
next prev parent reply other threads:[~2020-05-08 2:28 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-07 18:57 [PATCH] fs/io_uring: fix O_PATH fds in openat, openat2, statx Max Kellermann
2020-05-07 18:58 ` Jens Axboe
2020-05-07 19:01 ` Max Kellermann
2020-05-07 19:01 ` Al Viro
2020-05-07 19:05 ` Max Kellermann
2020-05-07 19:05 ` Jens Axboe
2020-05-07 19:12 ` Max Kellermann
2020-05-07 19:29 ` Al Viro
2020-05-07 19:37 ` Max Kellermann
2020-05-07 20:53 ` Jens Axboe
2020-05-07 22:06 ` Al Viro
2020-05-07 22:25 ` Jens Axboe
2020-05-07 22:44 ` Al Viro
2020-05-07 23:03 ` Jens Axboe
2020-05-07 23:31 ` Al Viro
2020-05-08 2:28 ` Jens Axboe [this message]
2020-05-08 2:53 ` Jens Axboe
[not found] ` <20200508152918.12340-1-hdanton@sina.com>
2020-05-08 15:33 ` Jens Axboe
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