Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1374685

Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup

From Linus Torvalds <torvalds@linux-foundation.org>
Newsgroups linux.kernel
Subject Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup
Date 2016-04-10 02:10 +0200
Message-ID <rmb6W-4QL-7@gated-at.bofh.it> (permalink)
References (3 earlier) <rlJX4-7e-27@gated-at.bofh.it> <rm0XT-5Cn-13@gated-at.bofh.it> <rm1TY-6j8-3@gated-at.bofh.it> <rm2wG-6Ee-3@gated-at.bofh.it> <rm9Rw-3Fp-15@gated-at.bofh.it>
Organization linux.* mail to news gateway

Show all headers | View raw

On Sat, Apr 9, 2016 at 3:37 PM, H. Peter Anvin <hpa@zytor.com> wrote:
>
> On the flipside, if we were to allow ourselves to break userspace, at this point I would suggest making /dev/pts/ptmx have a different device number and make the legacy /dev/ptmx print a warning message, after which it can at least eventually be deleted.

You don't need a different device number.

The /dev/pts/ptmx file may look like it's the same node as /dev/ptmx,
but it is trivial to recognize as the pts one:

     if (dentry->d_sb->s_magic == DEVPTS_SUPER_MAGIC)

and you're done.

But nobody actually uses /dev/pts/ptmx, because it has never had sane
permissions.

So the fact is, /dev/ptmx is what people use, and we're not breaking userspace.

But when we fix bad semantics (and always just looking up the initial
pts mount really is crazy semantics) that doesn't mean that we have to
bend over backwards to not make the changed semantics visible. We
don't _break_ user space, but we also don't care about some random
test-program that checks for particular semantics.

And I can pretty much _guarantee_ that nobody has ever done the "let's
bind-mount a 'ptmx' node in a /dev directory, and then expect that to
bind to some _other_ pts thing than the one in /dev/pts/".

Except as a test-program, or possibly as a "why the f*ck doesn't this
work? Oh, I need to use the single-instance thing because the
multi-instance pts thing is broken. Damn shitty implementation".

                Linus

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH 00/13] devpts: New instances for every mount ebiederm@xmission.com (Eric W. Biederman) - 2016-04-05 02:20 +0200
  [PATCH 04/13] devpts: Stop rolling devpts_remount by hand in devpts_mount "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
  [PATCH 05/13] devpts: Fail early (if appropriate) on overmount "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
  [PATCH 08/13] devpts: Make devpts_kill_sb safe if fsi is NULL "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
  [PATCH 03/13] devpts: Cleanup newinstance parsing "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
  [PATCH 06/13] devpts: Use the same default mode for both /dev/ptmx and dev/pts/ptmx "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
  [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
    [PATCH 09/13] devpts: Move the creation of /dev/pts/ptmx into fill_super "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
    [PATCH 02/13] devpts: More obvious check for the system devpts in pty allocation "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
    [PATCH 13/13] devpts: Kill the DEVPTS_MULTIPLE_INSTANCE config option "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
    [PATCH 07/13] devpts: Move parse_mount_options into fill_super "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
    [PATCH 12/13] devpts: Always return a distinct instance when mounting "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 04:00 +0200
    [PATCH 11/13] vfs: Implement mount_super_once "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 04:00 +0200
    [PATCH 10/13] devpts: Simplify devpts_mount by using mount_nodev "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 04:00 +0200
    Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Al Viro <viro@ZenIV.linux.org.uk> - 2016-04-05 05:00 +0200
      Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Al Viro <viro@ZenIV.linux.org.uk> - 2016-04-05 05:10 +0200
        Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-08 21:10 +0200
    Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-07 18:10 +0200
      Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-08 21:10 +0200
        Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-08 21:10 +0200
          Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-08 22:20 +0200
          Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Andy Lutomirski <luto@amacapital.net> - 2016-04-08 22:50 +0200
            Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-08 23:50 +0200
              Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Andy Lutomirski <luto@amacapital.net> - 2016-04-09 00:00 +0200
              Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-09 00:00 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-09 01:20 +0200
        Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-04-09 15:20 +0200
          Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup "H. Peter Anvin" <hpa@zytor.com> - 2016-04-09 16:20 +0200
            Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-09 17:00 +0200
              Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup "H. Peter Anvin" <hpa@zytor.com> - 2016-04-10 00:50 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-10 02:10 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup "H. Peter Anvin" <hpa@zytor.com> - 2016-04-10 02:20 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-10 02:20 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Andy Lutomirski <luto@amacapital.net> - 2016-04-10 02:50 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup "H. Peter Anvin" <hpa@zytor.com> - 2016-04-11 17:10 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Al Viro <viro@ZenIV.linux.org.uk> - 2016-04-12 03:40 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Andy Lutomirski <luto@amacapital.net> - 2016-04-11 22:20 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup "H. Peter Anvin" <hpa@zytor.com> - 2016-04-11 22:30 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-12 01:50 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-12 02:10 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-12 02:30 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-12 03:20 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup "H. Peter Anvin" <hpa@zytor.com> - 2016-04-12 03:20 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-12 03:40 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Al Viro <viro@ZenIV.linux.org.uk> - 2016-04-12 03:50 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Al Viro <viro@ZenIV.linux.org.uk> - 2016-04-12 03:40 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-12 04:30 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-11 22:30 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Andy Lutomirski <luto@amacapital.net> - 2016-04-12 19:50 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-12 20:20 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup "H. Peter Anvin" <hpa@zytor.com> - 2016-04-12 21:20 +0200
                [PATCH 01/16] devpts: Attempting to get it right ebiederm@xmission.com (Eric W. Biederman) - 2016-04-15 17:50 +0200
                [PATCH 08/16] devpts: Stop rolling devpts_remount by hand in devpts_mount "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 17:50 +0200
                [PATCH 05/16] vfs: Allow unlink, and rename on expirable file mounts "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 17:50 +0200
                [PATCH 04/16] devpts: Teach /dev/ptmx to automount the appropriate devpts via path lookup "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 17:50 +0200
                [PATCH 09/16] devpts: Fail early (if appropriate) on overmount "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 17:50 +0200
                [PATCH 10/16] devpts: Move parse_mount_options into fill_super "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 17:50 +0200
                [PATCH 06/16] devpts: More obvious check for the system devpts in pty allocation "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 17:50 +0200
                [PATCH 01/16] devpts: Use the same default mode for both /dev/ptmx and dev/pts/ptmx "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 17:50 +0200
                [PATCH 12/16] devpts: Move the creation of /dev/pts/ptmx into fill_super "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 18:00 +0200
                [PATCH 11/16] devpts: Make devpts_kill_sb safe if fsi is NULL "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 18:00 +0200
                [PATCH 16/16] devpts: Kill the DEVPTS_MULTIPLE_INSTANCE config option "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 18:00 +0200
                [PATCH 15/16] devpts: Always return a distinct instance when mounting "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 18:00 +0200
                [PATCH 13/16] devpts: Simplify devpts_mount by using mount_nodev "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 18:00 +0200
                [PATCH 14/16] vfs: Implement mount_super_once "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 18:00 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-12 02:10 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-12 02:10 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-12 02:40 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated  devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-12 03:00 +0200
                Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-11 22:20 +0200

csiph-web