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From: Jann Horn <jannh@google.com>
To: "Mickaël Salaün" <mic@digikod.net>
Cc: "James Morris" <jmorris@namei.org>,
	"Serge E . Hallyn" <serge@hallyn.com>,
	"Al Viro" <viro@zeniv.linux.org.uk>,
	"Andy Lutomirski" <luto@amacapital.net>,
	"Anton Ivanov" <anton.ivanov@cambridgegreys.com>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Casey Schaufler" <casey@schaufler-ca.com>,
	"Jeff Dike" <jdike@addtoit.com>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Kees Cook" <keescook@chromium.org>,
	"Michael Kerrisk" <mtk.manpages@gmail.com>,
	"Richard Weinberger" <richard@nod.at>,
	"Shuah Khan" <shuah@kernel.org>,
	"Vincent Dagonneau" <vincent.dagonneau@ssi.gouv.fr>,
	"Kernel Hardening" <kernel-hardening@lists.openwall.com>,
	"Linux API" <linux-api@vger.kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	"kernel list" <linux-kernel@vger.kernel.org>,
	"open list:KERNEL SELFTEST FRAMEWORK"
	<linux-kselftest@vger.kernel.org>,
	linux-security-module <linux-security-module@vger.kernel.org>,
	"the arch/x86 maintainers" <x86@kernel.org>,
	"Mickaël Salaün" <mic@linux.microsoft.com>
Subject: Re: [PATCH v24 01/12] landlock: Add object management
Date: Sat, 21 Nov 2020 08:00:00 +0100	[thread overview]
Message-ID: <CAG48ez0GryN4i0xCP22utLTqF5_o5J3nMBs+VC0DpQ+s09Bx6g@mail.gmail.com> (raw)
In-Reply-To: <20201112205141.775752-2-mic@digikod.net>

On Thu, Nov 12, 2020 at 9:51 PM Mickaël Salaün <mic@digikod.net> wrote:
> A Landlock object enables to identify a kernel object (e.g. an inode).
> A Landlock rule is a set of access rights allowed on an object.  Rules
> are grouped in rulesets that may be tied to a set of processes (i.e.
> subjects) to enforce a scoped access-control (i.e. a domain).
>
> Because Landlock's goal is to empower any process (especially
> unprivileged ones) to sandbox themselves, we cannot rely on a
> system-wide object identification such as file extended attributes.
> Indeed, we need innocuous, composable and modular access-controls.
>
> The main challenge with these constraints is to identify kernel objects
> while this identification is useful (i.e. when a security policy makes
> use of this object).  But this identification data should be freed once
> no policy is using it.  This ephemeral tagging should not and may not be
> written in the filesystem.  We then need to manage the lifetime of a
> rule according to the lifetime of its objects.  To avoid a global lock,
> this implementation make use of RCU and counters to safely reference
> objects.
>
> A following commit uses this generic object management for inodes.
>
> Cc: James Morris <jmorris@namei.org>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Serge E. Hallyn <serge@hallyn.com>
> Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
> Reviewed-by: Jann Horn <jannh@google.com>

Still looks good, except for one comment:

[...]
> +       /**
> +        * @lock: Guards against concurrent modifications.  This lock might be
> +        * held from the time @usage drops to zero until any weak references
> +        * from @underobj to this object have been cleaned up.
> +        *
> +        * Lock ordering: inode->i_lock nests inside this.
> +        */
> +       spinlock_t lock;

Why did you change this to "might be held" (v22 had "must")? Is the
"might" a typo?

  reply	other threads:[~2020-11-21  7:00 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-12 20:51 [PATCH v24 00/12] Landlock LSM Mickaël Salaün
2020-11-12 20:51 ` [PATCH v24 01/12] landlock: Add object management Mickaël Salaün
2020-11-21  7:00   ` Jann Horn [this message]
2020-11-21 10:11     ` Mickaël Salaün
2020-11-12 20:51 ` [PATCH v24 02/12] landlock: Add ruleset and domain management Mickaël Salaün
2020-11-20  1:52   ` James Morris
2020-11-21  7:00   ` Jann Horn
2020-11-21  9:45     ` Mickaël Salaün
2020-11-12 20:51 ` [PATCH v24 03/12] landlock: Set up the security framework and manage credentials Mickaël Salaün
2020-11-12 20:51 ` [PATCH v24 04/12] landlock: Add ptrace restrictions Mickaël Salaün
2020-11-12 20:51 ` [PATCH v24 05/12] LSM: Infrastructure management of the superblock Mickaël Salaün
2020-11-12 20:51 ` [PATCH v24 06/12] fs,security: Add sb_delete hook Mickaël Salaün
2020-11-12 20:51 ` [PATCH v24 07/12] landlock: Support filesystem access-control Mickaël Salaün
2020-11-21  7:00   ` Jann Horn
2020-11-21 10:06     ` Mickaël Salaün
2020-11-23 19:44       ` Jann Horn
2020-11-23 21:16         ` Mickaël Salaün
2020-11-23 21:19           ` Jann Horn
2020-11-12 20:51 ` [PATCH v24 08/12] landlock: Add syscall implementations Mickaël Salaün
2020-11-21  7:00   ` Jann Horn
2020-11-12 20:51 ` [PATCH v24 09/12] arch: Wire up Landlock syscalls Mickaël Salaün
2020-11-12 20:51 ` [PATCH v24 10/12] selftests/landlock: Add user space tests Mickaël Salaün
2020-11-12 20:51 ` [PATCH v24 11/12] samples/landlock: Add a sandbox manager example Mickaël Salaün
2020-11-12 20:51 ` [PATCH v24 12/12] landlock: Add user and kernel documentation Mickaël Salaün
2020-11-21  7:00   ` Jann Horn
2020-11-24  2:38     ` James Morris
2020-11-17  5:37 ` [PATCH v24 00/12] Landlock LSM James Morris

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