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From: Josh Triplett <[email protected]>
To: Jens Axboe <[email protected]>
Cc: [email protected], [email protected]
Subject: Re: [PATCH 6/6] io_uring: allow specific fd for IORING_OP_ACCEPT
Date: Wed, 4 Mar 2020 11:02:23 -0800	[thread overview]
Message-ID: <20200304190223.GA16251@localhost> (raw)
In-Reply-To: <[email protected]>

On Wed, Mar 04, 2020 at 11:00:16AM -0700, Jens Axboe wrote:
> sqe->len can be set to a specific fd we want to use for accept4(), so
> it uses that one instead of just assigning a free unused one.
[...]
> +	accept->open_fd = READ_ONCE(sqe->len);
> +	if (!accept->open_fd)
> +		accept->open_fd = -1;

0 is a valid file descriptor. I realize that it seems unlikely, but I
went to a fair bit of trouble in my patch series to ensure that
userspace could use any valid file descriptor openat2, without a corner
case like "you can't open as file descriptor 0", even though it would
have been more convenient to just say "if you pass a non-zero fd in
open_how". Please consider accepting a flag to determine the validity of
open_fd.

- Josh Triplett

  reply	other threads:[~2020-03-04 19:02 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-04 18:00 [PATCHSET v2 0/6] Support selectable file descriptors Jens Axboe
2020-03-04 18:00 ` [PATCH 1/6] fs: openat2: Extend open_how to allow userspace-selected fds Jens Axboe
2020-03-04 18:00 ` [PATCH 2/6] io_uring: move CLOSE req->file checking into handler Jens Axboe
2020-03-04 18:00 ` [PATCH 3/6] io_uring: move read/write side file based prep into op handler Jens Axboe
2020-03-04 18:00 ` [PATCH 4/6] io_uring: support deferred retrival of file from fd Jens Axboe
2020-03-04 18:00 ` [PATCH 5/6] net: allow specific fd selection for __sys_accept4_file() Jens Axboe
2020-03-04 18:00 ` [PATCH 6/6] io_uring: allow specific fd for IORING_OP_ACCEPT Jens Axboe
2020-03-04 19:02   ` Josh Triplett [this message]
2020-03-04 19:09     ` Jens Axboe
2020-03-04 19:51       ` Josh Triplett
2020-03-04 19:03 ` [PATCHSET v2 0/6] Support selectable file descriptors Josh Triplett
2020-03-04 19:10   ` Jens Axboe
2020-03-04 19:28     ` Jeff Layton
2020-03-04 19:50       ` Jens Axboe
2020-03-04 19:56     ` Josh Triplett
2020-03-04 20:00       ` Jens Axboe
2020-03-04 20:09         ` Josh Triplett
2020-03-04 20:14           ` Jens Axboe
2020-03-09 20:33 ` Stefan Metzmacher

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