From: Miklos Szeredi <miklos@szeredi.hu>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Jann Horn <jannh@google.com>,
Casey Schaufler <casey@schaufler-ca.com>,
Andy Lutomirski <luto@amacapital.net>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
David Howells <dhowells@redhat.com>, Karel Zak <kzak@redhat.com>,
Jeff Layton <jlayton@redhat.com>,
Miklos Szeredi <mszeredi@redhat.com>,
Nicolas Dichtel <nicolas.dichtel@6wind.com>,
Christian Brauner <christian@brauner.io>,
Lennart Poettering <lennart@poettering.net>,
Linux API <linux-api@vger.kernel.org>,
Ian Kent <raven@themaw.net>,
LSM <linux-security-module@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: file metadata via fs API (was: [GIT PULL] Filesystem Information)
Date: Tue, 18 Aug 2020 11:30:30 +0200 [thread overview]
Message-ID: <CAJfpegs2EkMNthnMvdr5NtLKxfQjTgJYSNhHOMROm0S98OJb4A@mail.gmail.com> (raw)
In-Reply-To: <20200812183326.GU1236603@ZenIV.linux.org.uk>
On Wed, Aug 12, 2020 at 8:33 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> On Wed, Aug 12, 2020 at 06:39:11PM +0100, Al Viro wrote:
> > On Wed, Aug 12, 2020 at 07:16:37PM +0200, Miklos Szeredi wrote:
> > > On Wed, Aug 12, 2020 at 6:33 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
> > > >
> > > > On Wed, Aug 12, 2020 at 05:13:14PM +0200, Miklos Szeredi wrote:
> > >
> > > > > Why does it have to have a struct mount? It does not have to use
> > > > > dentry/mount based path lookup.
> > > >
> > > > What the fuck? So we suddenly get an additional class of objects
> > > > serving as kinda-sorta analogues of dentries *AND* now struct file
> > > > might refer to that instead of a dentry/mount pair - all on the VFS
> > > > level? And so do all the syscalls you want to allow for such "pathnames"?
> > >
> > > The only syscall I'd want to allow is open, everything else would be
> > > on the open files themselves.
> > >
> > > file->f_path can refer to an anon mount/inode, the real object is
> > > referred to by file->private_data.
> > >
> > > The change to namei.c would be on the order of ~10 lines. No other
> > > parts of the VFS would be affected.
> >
> > If some of the things you open are directories (and you *have* said that
> > directories will be among those just upthread, and used references to
> > readdir() as argument in favour of your approach elsewhere in the thread),
> > you will have to do something about fchdir(). And that's the least of
> > the issues.
>
> BTW, what would such opened files look like from /proc/*/fd/* POV? And
> what would happen if you walk _through_ that symlink, with e.g. ".."
> following it? Or with names of those attributes, for that matter...
> What about a normal open() of such a sucker? It won't know where to
> look for your ->private_data...
>
> FWIW, you keep refering to regularity of this stuff from the syscall
> POV, but it looks like you have no real idea of what subset of the
> things available for normal descriptors will be available for those.
I have said that IMO using a non-seekable anon-file would be okay for
those. All the answers fall out of that: nothing works on those
fd's except read/write/getdents. No fchdir(), no /proc/*/fd deref,
etc...
Starting with a very limited functionality and expanding on that if
necessary is I think a good way to not get bogged down with the
details.
Thanks,
Miklos
next prev parent reply other threads:[~2020-08-18 9:30 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-03 15:27 [GIT PULL] Mount notifications David Howells
2020-08-03 15:49 ` [GIT PULL] Filesystem Information David Howells
2020-08-03 16:42 ` Miklos Szeredi
2020-08-04 2:15 ` Ian Kent
2020-08-04 14:36 ` Miklos Szeredi
2020-08-05 1:33 ` Ian Kent
2020-08-05 8:00 ` Miklos Szeredi
2020-08-05 11:13 ` Ian Kent
2020-08-05 8:24 ` file metadata via fs API (was: [GIT PULL] Filesystem Information) Miklos Szeredi
2020-08-11 13:54 ` Miklos Szeredi
2020-08-11 14:08 ` Al Viro
2020-08-11 14:22 ` Miklos Szeredi
2020-08-11 14:31 ` Al Viro
[not found] ` <CAAgocE07=vVKpQhG+rjEGO=NEBKZ02gjg4TRPxECAc+RKrzn=Q@mail.gmail.com>
2020-08-11 14:36 ` Al Viro
2020-08-11 14:36 ` Miklos Szeredi
2020-08-11 14:42 ` Al Viro
2020-08-11 14:47 ` Miklos Szeredi
2020-08-11 15:20 ` Linus Torvalds
2020-08-11 15:30 ` Miklos Szeredi
2020-08-11 16:05 ` Linus Torvalds
2020-08-11 18:49 ` Miklos Szeredi
2020-08-11 19:31 ` Lennart Poettering
2020-08-11 19:50 ` Christian Brauner
2020-08-11 19:39 ` Christian Brauner
2020-08-12 0:53 ` Ian Kent
2020-08-11 15:39 ` Andy Lutomirski
2020-08-11 16:17 ` Casey Schaufler
2020-08-11 16:30 ` Linus Torvalds
2020-08-11 20:28 ` Miklos Szeredi
2020-08-11 20:36 ` Jann Horn
2020-08-11 20:56 ` Miklos Szeredi
2020-08-11 21:17 ` Andy Lutomirski
2020-08-11 21:18 ` Linus Torvalds
2020-08-12 7:23 ` Miklos Szeredi
2020-08-12 14:39 ` Al Viro
2020-08-12 14:46 ` Miklos Szeredi
2020-08-12 15:08 ` Al Viro
2020-08-12 15:13 ` Miklos Szeredi
2020-08-12 16:33 ` Al Viro
2020-08-12 17:16 ` Miklos Szeredi
2020-08-12 17:39 ` Al Viro
2020-08-12 18:33 ` Al Viro
2020-08-12 21:30 ` Al Viro
2020-08-18 9:41 ` Miklos Szeredi
2020-08-18 9:30 ` Miklos Szeredi [this message]
2020-08-12 15:22 ` David Howells
2020-08-11 21:20 ` Al Viro
2020-08-11 21:35 ` Casey Schaufler
2020-08-11 16:05 ` Al Viro
2020-08-11 16:09 ` Linus Torvalds
2020-08-11 16:39 ` Al Viro
2020-08-12 10:14 ` Karel Zak
2020-08-12 13:09 ` Miklos Szeredi
2020-08-12 13:33 ` David Howells
2020-08-12 13:54 ` Miklos Szeredi
2020-08-12 0:05 ` David Howells
2020-08-12 7:55 ` Miklos Szeredi
2020-08-12 8:29 ` David Howells
2020-08-12 8:37 ` Miklos Szeredi
2020-08-12 9:43 ` file metadata via fs API Steven Whitehouse
2020-08-12 10:04 ` Miklos Szeredi
2020-08-12 11:28 ` Karel Zak
2020-08-12 12:43 ` Miklos Szeredi
2020-08-13 8:52 ` Karel Zak
2020-08-12 13:06 ` David Howells
2020-08-13 1:01 ` Ian Kent
2020-08-12 18:18 ` file metadata via fs API (was: [GIT PULL] Filesystem Information) Linus Torvalds
2020-08-12 19:34 ` file metadata via fs API Steven Whitehouse
2020-08-12 19:50 ` Linus Torvalds
2020-08-13 3:44 ` Ian Kent
2020-08-13 10:36 ` Karel Zak
2020-08-14 7:58 ` Lennart Poettering
2020-08-17 11:32 ` Steven Whitehouse
2020-08-17 17:15 ` Linus Torvalds
2020-08-17 22:44 ` Linus Torvalds
2020-08-18 12:50 ` Miklos Szeredi
2020-08-18 18:51 ` Linus Torvalds
2020-08-18 20:18 ` Miklos Szeredi
2020-08-18 20:53 ` Linus Torvalds
2020-08-21 13:17 ` Miklos Szeredi
2020-08-19 2:29 ` Al Viro
2020-08-13 3:53 ` file metadata via fs API (was: [GIT PULL] Filesystem Information) Jeffrey E Altman
2020-08-14 17:05 ` Linus Torvalds
2020-08-18 15:01 ` Jeffrey E Altman
2020-08-14 8:06 ` Lennart Poettering
2020-08-12 13:54 ` David Howells
2020-08-12 14:10 ` Miklos Szeredi
2020-08-12 14:23 ` David Howells
2020-08-03 22:48 ` [GIT PULL] Mount notifications Ian Kent
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