linux-kernel - Re: file metadata via fs API

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <989bb93754a4af69c02a9f42b05549f7e72630b3.camel@themaw.net>
Date:   Thu, 13 Aug 2020 09:01:31 +0800
From:   Ian Kent <raven@...maw.net>
To:     David Howells <dhowells@...hat.com>,
        Miklos Szeredi <miklos@...redi.hu>
Cc:     Karel Zak <kzak@...hat.com>,
        Steven Whitehouse <swhiteho@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Jeff Layton <jlayton@...hat.com>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Nicolas Dichtel <nicolas.dichtel@...nd.com>,
        Christian Brauner <christian@...uner.io>,
        Lennart Poettering <lennart@...ttering.net>,
        Linux API <linux-api@...r.kernel.org>,
        LSM <linux-security-module@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: file metadata via fs API

On Wed, 2020-08-12 at 14:06 +0100, David Howells wrote:
> Miklos Szeredi <miklos@...redi.hu> wrote:
> 
> > That presumably means the mount ID <-> mount path mapping already
> > exists, which means it's just possible to use the open(mount_path,
> > O_PATH) to obtain the base fd.
> 
> No, you can't.  A path more correspond to multiple mounts stacked on
> top of
> each other, e.g.:
> 
> 	mount -t tmpfs none /mnt
> 	mount -t tmpfs none /mnt
> 	mount -t tmpfs none /mnt
> 
> Now you have three co-located mounts and you can't use the path to
> differentiate them.  I think this might be an issue in autofs, but
> Ian would
> need to comment on that.

It is a problem for autofs, direct mounts in particular, but also
for mount ordering at times when umounting a tree of mounts where
mounts are covered or at shutdown.

Ian