linux-fsdevel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Miklos Szeredi <miklos@szeredi.hu>
To: Simon Ser <contact@emersion.fr>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
Subject: Re: procfs: open("/proc/self/fd/...") allows bypassing O_RDONLY
Date: Thu, 12 May 2022 14:56:22 +0200	[thread overview]
Message-ID: <CAJfpegs4GVirNVtf4OqunzNwbXQywZVkxpGPtpN=ZonHU2SpiA@mail.gmail.com> (raw)
In-Reply-To: <03l0hfZIzD9KwSxSntGcmfFhvbIKiK45poGUhXtR7Qi0Av0-ZnqnSBPAP09GGpSrKGZWZNCTvme_Gpiuz0Bcg6ewDIXSH24SBx_tvfyZSWU=@emersion.fr>

On Thu, 12 May 2022 at 14:41, Simon Ser <contact@emersion.fr> wrote:
>
> On Thursday, May 12th, 2022 at 12:37, Simon Ser <contact@emersion.fr> wrote:
>
> > what would be a good way to share a FD to another
> > process without allowing it to write to the underlying file?
>
> (I'm reminded that memfd + seals exist for this purpose. Still, I'd be
> interested to know whether that O_RDONLY/O_RDWR behavior is intended,
> because it's pretty surprising. The motivation for using O_RDONLY over
> memfd seals is that it isn't Linux-specific.)

Yes, this is intended.   The /proc/$PID/fd/$FD file represents the
inode pointed to by $FD.   So the open flags for $FD are irrelevant
when operating on the proc fd file.

Thanks,
Miklos

  reply	other threads:[~2022-05-12 12:56 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-12 10:37 procfs: open("/proc/self/fd/...") allows bypassing O_RDONLY Simon Ser
2022-05-12 12:30 ` Amir Goldstein
2022-05-12 12:38   ` Simon Ser
2022-05-13  9:36     ` Amir Goldstein
2022-05-16  7:51     ` Rasmus Villemoes
2022-05-12 12:41 ` Simon Ser
2022-05-12 12:56   ` Miklos Szeredi [this message]
2022-05-13  9:58     ` Christian Brauner
2022-05-26 13:03       ` Aleksa Sarai
2022-05-26 11:08 ` Pavel Machek
2022-05-26 13:09 ` Aleksa Sarai

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='CAJfpegs4GVirNVtf4OqunzNwbXQywZVkxpGPtpN=ZonHU2SpiA@mail.gmail.com' \
    --to=miklos@szeredi.hu \
    --cc=contact@emersion.fr \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    /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;
as well as URLs for NNTP newsgroup(s).