linux-kernel - Re: [PATCH -next 0/5] landlock: add chmod and chown support

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Date:   Mon, 22 Aug 2022 12:35:18 -0700
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     Günther Noack <gnoack3000@...il.com>,
        Xiu Jianfeng <xiujianfeng@...wei.com>
Cc:     mic@...ikod.net, paul@...l-moore.com, jmorris@...ei.org,
        serge@...lyn.com, shuah@...nel.org, corbet@....net,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-doc@...r.kernel.org, casey@...aufler-ca.com
Subject: Re: [PATCH -next 0/5] landlock: add chmod and chown support

On 8/22/2022 12:17 PM, Günther Noack wrote:
> Hi!
>
> Very exciting to see! Thank you for sending this! :)
>
> I'm just throwing in some comments based on the very similar truncate
> patch set, in the hope that it helps. (But obviously, Mickaël Salaün
> has the last word on this code.)
>
> Slightly higher level question: Should we start to group the
> functionality of multiple LSM hooks under one Landlock flag? (Will it
> be harder to change the LSM hook interface in the future if we
> continue to add one flag per hook? Or is this structure already
> exposed to userspace by other LSMs?)

I'm not a landlock expert. The question is nonsensical, yet somewhat
frightening nonetheless. Could you put just a touch more context into
what you're asking for?

> For example, some of the "missing" operations listed on the Landlock
> documentation could also be grouped roughly as:
>
> Modifying files:
>  - truncate
>
> Modifying file metadata:
>  - chmod
>  - chown
>  - setxattr
>  - utime
>
> Observing files (check presence and file metadata):
>  - access
>  - stat
>  - readlink, following links (can observe symlink presence)
>  - chdir (can observe dir presence and 'x' attribute)
>
> Ungrouped:
>  - flock
>  - ioctl
>  - fcntl
>
> Do you have opinions on this?
>
> —Günther
>
> On Mon, Aug 22, 2022 at 07:46:56PM +0800, Xiu Jianfeng wrote:
>> hi,
>>   this patchset adds chmod and chown support for landlock
>>
>> Xiu Jianfeng (5):
>>   landlock: expand access_mask_t to u32 type
>>   landlock: add chmod and chown support
>>   landlock/selftests: add selftests for chmod and chown
>>   landlock/samples: add chmod and chown support
>>   landlock: update chmod and chown support in document
>>
>>  Documentation/userspace-api/landlock.rst     |   8 +-
>>  include/uapi/linux/landlock.h                |   8 +-
>>  samples/landlock/sandboxer.c                 |  12 +-
>>  security/landlock/fs.c                       |  16 +-
>>  security/landlock/limits.h                   |   2 +-
>>  security/landlock/ruleset.h                  |   2 +-
>>  security/landlock/syscalls.c                 |   2 +-
>>  tools/testing/selftests/landlock/base_test.c |   2 +-
>>  tools/testing/selftests/landlock/fs_test.c   | 234 ++++++++++++++++++-
>>  9 files changed, 274 insertions(+), 12 deletions(-)
>>
>> --
>> 2.17.1
>>
> --