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From: Kees Cook <keescook@chromium.org>
To: Casey Schaufler <casey@schaufler-ca.com>
Cc: "Mickaël Salaün" <mic@digikod.net>,
	LKML <linux-kernel@vger.kernel.org>,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Andy Lutomirski" <luto@amacapital.net>,
	"Arnaldo Carvalho de Melo" <acme@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"David Drysdale" <drysdale@google.com>,
	"David S . Miller" <davem@davemloft.net>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	"James Morris" <james.l.morris@oracle.com>,
	"Jann Horn" <jann@thejh.net>, "Jonathan Corbet" <corbet@lwn.net>,
	"Matthew Garrett" <mjg59@srcf.ucam.org>,
	"Michael Kerrisk" <mtk.manpages@gmail.com>,
	"Paul Moore" <paul@paul-moore.com>,
	"Sargun Dhillon" <sargun@sargun.me>,
	"Serge E . Hallyn" <serge@hallyn.com>,
	"Shuah Khan" <shuah@kernel.org>, "Tejun Heo" <tj@kernel.org>,
	"Thomas Graf" <tgraf@suug.ch>, "Will Drewry" <wad@chromium.org>,
	"kernel-hardening@lists.openwall.com"
	<kernel-hardening@lists.openwall.com>,
	"Linux API" <linux-api@vger.kernel.org>,
	linux-security-module <linux-security-module@vger.kernel.org>,
	"Network Development" <netdev@vger.kernel.org>
Subject: Re: [PATCH net-next v6 04/11] landlock: Add LSM hooks related to filesystem
Date: Tue, 18 Apr 2017 16:40:34 -0700	[thread overview]
Message-ID: <CAGXu5jKCr1qPqJ8YWAjK1Lj-fThAhMnrxFW8twFcj6C9ODBpsA@mail.gmail.com> (raw)
In-Reply-To: <c122415d-c2be-d013-efb4-833ba87d144d@schaufler-ca.com>

On Tue, Apr 18, 2017 at 4:16 PM, Casey Schaufler <casey@schaufler-ca.com> wrote:
> On 4/18/2017 3:44 PM, Mickaël Salaün wrote:
>> On 19/04/2017 00:17, Kees Cook wrote:
>>> On Tue, Mar 28, 2017 at 4:46 PM, Mickaël Salaün <mic@digikod.net> wrote:
>>>> +void __init landlock_add_hooks(void)
>>>> +{
>>>> +       pr_info("landlock: Version %u", LANDLOCK_VERSION);
>>>> +       landlock_add_hooks_fs();
>>>> +       security_add_hooks(NULL, 0, "landlock");
>>>> +       bpf_register_prog_type(&bpf_landlock_type);
>>> I'm confused by the separation of hook registration here. The call to
>>> security_add_hooks is with count=0 is especially weird. Why isn't this
>>> just a single call with security_add_hooks(landlock_hooks,
>>> ARRAY_SIZE(landlock_hooks), "landlock")?
>> Yes, this is ugly with the new security_add_hooks() with three arguments
>> but I wanted to split the hooks definition in multiple files.
>
> Why? I'll buy a good argument, but there are dangers in
> allowing multiple calls to security_add_hooks().
>
>>
>> The current security_add_hooks() use lsm_append(lsm, &lsm_names) which
>> is not exported. Unfortunately, calling multiple security_add_hooks()
>> with the same LSM name would register multiple names for the same LSM…
>> Is it OK if I modify this function to not add duplicated entries?
>
> It may seem absurd, but it's conceivable that a module might
> have two hooks it wants called. My example is a module that
> counts the number of times SELinux denies a process access to
> things (which needs to be called before and after SELinux in
> order to detect denials) and takes "appropriate action" if
> too many denials occur. It would be weird, wonky and hackish,
> but that never stopped anybody before.

If ends up being sane and clear, I'm fine with allowing multiple calls.

-Kees

-- 
Kees Cook
Pixel Security

  reply	other threads:[~2017-04-18 23:40 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-28 23:46 [PATCH net-next v6 00/11] Landlock LSM: Toward unprivileged sandboxing Mickaël Salaün
2017-03-28 23:46 ` [PATCH net-next v6 01/11] bpf: Add eBPF program subtype and is_valid_subtype() verifier Mickaël Salaün
2017-03-29 13:48   ` kbuild test robot
2017-04-18 21:48   ` Kees Cook
2017-03-28 23:46 ` [PATCH net-next v6 02/11] bpf,landlock: Define an eBPF program type for Landlock Mickaël Salaün
2017-04-16 21:57   ` Mickaël Salaün
2017-04-18 21:58   ` Kees Cook
2017-03-28 23:46 ` [PATCH net-next v6 03/11] bpf: Define handle_fs and add a new helper bpf_handle_fs_get_mode() Mickaël Salaün
2017-03-28 23:46 ` [PATCH net-next v6 04/11] landlock: Add LSM hooks related to filesystem Mickaël Salaün
2017-03-29 15:18   ` kbuild test robot
2017-04-18 22:17   ` Kees Cook
2017-04-18 22:44     ` Mickaël Salaün
2017-04-18 23:16       ` Casey Schaufler
2017-04-18 23:40         ` Kees Cook [this message]
2017-04-19 22:03           ` Mickaël Salaün
2017-04-19 23:58             ` [kernel-hardening] " Casey Schaufler
2017-04-20  1:48             ` Kees Cook
2017-04-18 23:39       ` Kees Cook
2017-03-28 23:46 ` [PATCH net-next v6 05/11] seccomp: Split put_seccomp_filter() with put_seccomp() Mickaël Salaün
2017-04-18 22:23   ` Kees Cook
2017-04-18 22:47     ` Mickaël Salaün
2017-04-19 22:18       ` Mickaël Salaün
2017-04-20  1:54         ` Kees Cook
2017-03-28 23:46 ` [PATCH net-next v6 06/11] seccomp,landlock: Handle Landlock events per process hierarchy Mickaël Salaün
2017-03-29 10:35   ` [kernel-hardening] " Djalal Harouni
2017-03-31 21:15     ` Mickaël Salaün
2017-04-18 22:54       ` Kees Cook
2017-04-18 22:53   ` Kees Cook
2017-04-18 23:24     ` Mickaël Salaün
2017-04-18 23:48       ` Kees Cook
2017-03-28 23:46 ` [PATCH net-next v6 07/11] landlock: Add ptrace restrictions Mickaël Salaün
2017-04-10  6:48   ` [kernel-hardening] " Djalal Harouni
2017-04-11  7:19     ` Mickaël Salaün
2017-03-28 23:46 ` [PATCH net-next v6 08/11] bpf: Add a Landlock sandbox example Mickaël Salaün
2017-04-18 23:06   ` Kees Cook
2017-04-18 23:35     ` Mickaël Salaün
2017-03-28 23:46 ` [PATCH net-next v6 09/11] seccomp: Enhance test_harness with an assert step mechanism Mickaël Salaün
2017-04-19  0:02   ` Kees Cook
2017-04-19 21:51     ` Mickaël Salaün
2017-04-19 22:02       ` Kees Cook
2017-04-19 22:05         ` Mickaël Salaün
2017-04-20  1:50           ` Kees Cook
2017-03-28 23:46 ` [PATCH net-next v6 10/11] bpf,landlock: Add tests for Landlock Mickaël Salaün
2017-04-18 23:16   ` Kees Cook
2017-04-18 23:53     ` Mickaël Salaün
2017-04-18 23:59       ` Kees Cook
2017-03-28 23:46 ` [PATCH net-next v6 11/11] landlock: Add user and kernel documentation " Mickaël Salaün
2017-03-29 15:58   ` kbuild test robot
2017-04-18 23:26 ` [PATCH net-next v6 00/11] Landlock LSM: Toward unprivileged sandboxing Kees Cook
2017-04-19  0:12   ` Mickaël Salaün

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