From: Christian Brauner <brauner@kernel.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
linux-fsdevel@vger.kernel.org
Subject: Re: [RFC] possible way to deal with dup2() vs. allocated but still not opened descriptors
Date: Wed, 5 Jun 2024 16:23:14 +0200 [thread overview]
Message-ID: <20240605-strategisch-walten-40bc8601984e@brauner> (raw)
In-Reply-To: <20240605022855.GV1629371@ZenIV>
On Wed, Jun 05, 2024 at 03:28:55AM +0100, Al Viro wrote:
> dup2(old, new) has an unpleasant corner case - when new has been
> already reserved by e.g. open() from another thread, but that open()
> still didn't get to installing an opened file to that descriptor.
>
> It's outside of POSIX scope and any userland code that might
> run into it is buggy. However, we need to make sure that nothing breaks
> kernel-side. We used to have interesting bugs in that area and so did
> *BSD kernels.
>
> Current solution is to have dup2() fail with -EBUSY. However,
> there's an approach that might avoid that wart. I'm not sure whether
> it's worth bothering with - it will have a cost, but then it might reduce
> the pingpong on current->files->file_lock.
Fwiw, doesn't seem worth the trouble and would likely just complicate
things for something that we've never really heard being a problem.
prev parent reply other threads:[~2024-06-05 14:23 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-05 2:28 [RFC] possible way to deal with dup2() vs. allocated but still not opened descriptors Al Viro
2024-06-05 2:39 ` Al Viro
2024-06-05 14:23 ` Christian Brauner [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20240605-strategisch-walten-40bc8601984e@brauner \
--to=brauner@kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=torvalds@linux-foundation.org \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox