From: Andy Lutomirski <luto@kernel.org>
To: Aleksa Sarai <cyphar@cyphar.com>
Cc: "Stas Sergeev" <stsp2@yandex.ru>,
"Serge E. Hallyn" <serge@hallyn.com>,
linux-kernel@vger.kernel.org,
"Stefan Metzmacher" <metze@samba.org>,
"Eric Biederman" <ebiederm@xmission.com>,
"Alexander Viro" <viro@zeniv.linux.org.uk>,
"Andy Lutomirski" <luto@kernel.org>,
"Christian Brauner" <brauner@kernel.org>,
"Jan Kara" <jack@suse.cz>, "Jeff Layton" <jlayton@kernel.org>,
"Chuck Lever" <chuck.lever@oracle.com>,
"Alexander Aring" <alex.aring@gmail.com>,
"David Laight" <David.Laight@aculab.com>,
linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Christian Göttsche" <cgzones@googlemail.com>
Subject: Re: [PATCH v5 0/3] implement OA2_CRED_INHERIT flag for openat2()
Date: Mon, 6 May 2024 10:34:16 -0700 [thread overview]
Message-ID: <CALCETrUZp2P1PXwJeL7ryda_qSLGsgHf5X0Zpw8piiT58k-cYg@mail.gmail.com> (raw)
In-Reply-To: <CALCETrU2VwCF-o7E5sc8FN_LBs3Q-vNMBf7N4rm0PAWFRo5QWw@mail.gmail.com>
On Mon, May 6, 2024 at 10:29 AM Andy Lutomirski <luto@amacapital.net> wrote:
>
> Replying to a couple emails at once...
>
> On Mon, May 6, 2024 at 12:14 AM Aleksa Sarai <cyphar@cyphar.com> wrote:
> > I also find it somewhat amusing that this proposal is to basically give
> > up on multi-user permissions for this one directory tree because it's
> > too annoying to deal with. In that case, isn't chmod 777 a simpler
> > solution? (I'm being a bit flippant, of course there is a difference,
> > but the net result is that all users in the container would have the
> > same permissions with all of the fun issues that implies.)
> >
> > In short, AFAICS idmapped mounts pretty much solve this problem (minus
> > the ability to collapse users, which I suspect is not a good idea in
> > general)?
> >
>
> With my kernel hat on, maybe I agree. But with my *user* hat on, I
> think I pretty strongly disagree. Look, idmapis lousy for
> unprivileged use:
>
> $ install -m 0700 -d test_directory
> $ echo 'hi there' >test_directory/file
> $ podman run -it --rm
> --mount=type=bind,src=test_directory,dst=/tmp,idmap [debian-slim]
> # cat /tmp/file
> hi there
>
> <-- Hey, look, this kind of works!
>
> # setpriv --reuid=1 ls /tmp
> ls: cannot open directory '/tmp': Permission denied
>
> <-- Gee, thanks, Linux!
I should add: this is lousy even for privileged use. On a normal
non-containerized system:
$ ls -ld /var/lib/mysql
drwxr-xr-x. 3 mysql mysql 4096 Sep 20 2023 /var/lib/mysql
This makes perfect sense.
But if I want to run mysql in a container in a sane way, my only real
choice is either to trust the container manager quite strongly (so it
only maps this directory into the correct container) or, if I want to
separate out management of this container into its own UID (which is a
good practice), then I'm forced to do some kind of fragile hack like
making a directory only accessible to the correct UID and then
creating a 0777 directory inside it and bind-mounting *that*.
next prev parent reply other threads:[~2024-05-06 17:34 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-26 13:33 [PATCH v5 0/3] implement OA2_CRED_INHERIT flag for openat2() Stas Sergeev
2024-04-26 13:33 ` [PATCH v5 1/3] fs: reorganize path_openat() Stas Sergeev
2024-04-26 13:33 ` [PATCH v5 2/3] open: add O_CRED_ALLOW flag Stas Sergeev
2024-04-27 2:12 ` kernel test robot
2024-04-26 13:33 ` [PATCH v5 3/3] openat2: add OA2_CRED_INHERIT flag Stas Sergeev
2024-04-28 16:41 ` [PATCH v5 0/3] implement OA2_CRED_INHERIT flag for openat2() Andy Lutomirski
2024-04-28 17:39 ` stsp
2024-04-28 19:15 ` stsp
2024-04-28 20:19 ` Andy Lutomirski
2024-04-28 21:14 ` stsp
2024-04-28 21:30 ` Andy Lutomirski
2024-04-28 22:12 ` stsp
2024-04-29 1:12 ` stsp
2024-04-29 9:12 ` Christian Brauner
2024-05-06 7:13 ` Aleksa Sarai
2024-05-06 17:29 ` Andy Lutomirski
2024-05-06 17:34 ` Andy Lutomirski [this message]
2024-05-06 19:34 ` David Laight
2024-05-06 21:53 ` Andy Lutomirski
2024-05-07 7:42 ` Christian Brauner
2024-05-07 20:38 ` Andy Lutomirski
2024-05-08 7:32 ` Christian Brauner
2024-05-08 17:30 ` Andy Lutomirski
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