linux-kernel - Re: [PATCH v1 0/5] Landlock support for UML

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Date:   Tue, 21 Mar 2023 22:18:15 +0100
From:   Mickaël Salaün <mic@...ikod.net>
To:     Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        Richard Weinberger <richard@....at>
Cc:     Christopher Obbard <chris.obbard@...labora.com>,
        Guenter Roeck <groeck@...omium.org>,
        Günther Noack <gnoack3000@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        James Morris <jmorris@...ei.org>, Jeff Xu <jeffxu@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Paul Moore <paul@...l-moore.com>,
        Ritesh Raj Sarraf <ritesh@...labora.com>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Sjoerd Simons <sjoerd@...labora.com>,
        Willem de Bruijn <willemb@...gle.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Christian Brauner <brauner@...nel.org>
Subject: Re: [PATCH v1 0/5] Landlock support for UML

Richard, Anton, Johannes, what do you think about these UML changes?


On 09/03/2023 17:54, Mickaël Salaün wrote:
> Hi,
> 
> Commit cb2c7d1a1776 ("landlock: Support filesystem access-control")
> introduced a new ARCH_EPHEMERAL_INODES configuration, only enabled for
> User-Mode Linux.  The reason was that UML's hostfs managed inodes in an
> ephemeral way: from the kernel point of view, the same inode struct
> could be created several times while being used by user space because
> the kernel didn't hold references to inodes.  Because Landlock (and
> probably other subsystems) ties properties (i.e. access rights) to inode
> objects, it wasn't possible to create rules that match inodes and then
> allow specific accesses.
> 
> This patch series fixes the way UML manages inodes according to the
> underlying filesystem.  They are now properly handles as for other
> filesystems, which enables to support Landlock (and probably other
> features).
> 
> Backporting these patches requires some selftest harness patches
> backports too.
> 
> Regards,
> 
> Mickaël Salaün (5):
>    hostfs: Fix ephemeral inodes
>    selftests/landlock: Don't create useless file layouts
>    selftests/landlock: Add supports_filesystem() helper
>    selftests/landlock: Make mounts configurable
>    selftests/landlock: Add tests for pseudo filesystems
> 
>   arch/Kconfig                               |   7 -
>   arch/um/Kconfig                            |   1 -
>   fs/hostfs/hostfs.h                         |   1 +
>   fs/hostfs/hostfs_kern.c                    | 213 ++++++------
>   fs/hostfs/hostfs_user.c                    |   1 +
>   security/landlock/Kconfig                  |   2 +-
>   tools/testing/selftests/landlock/config    |   8 +-
>   tools/testing/selftests/landlock/fs_test.c | 381 +++++++++++++++++++--
>   8 files changed, 472 insertions(+), 142 deletions(-)
> 
> 
> base-commit: fe15c26ee26efa11741a7b632e9f23b01aca4cc6