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 v22 01/12] landlock: Add object management
Date: Thu, 29 Oct 2020 02:05:47 +0100 [thread overview]
Message-ID: <CAG48ez3CKa12SFHjVUPnYzJm2E7OBWnuh3JzVMrsvqdcMS1A8A@mail.gmail.com> (raw)
In-Reply-To: <20201027200358.557003-2-mic@digikod.net>
On Tue, Oct 27, 2020 at 9:04 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: Jann Horn <jannh@google.com>
> 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>
except for some minor nits:
[...]
> diff --git a/security/landlock/object.c b/security/landlock/object.c
[...]
> +void landlock_put_object(struct landlock_object *const object)
> +{
> + /*
> + * The call to @object->underops->release(object) might sleep e.g.,
s/ e.g.,/, e.g./
> + * because of iput().
> + */
> + might_sleep();
> + if (!object)
> + return;
[...]
> +}
> diff --git a/security/landlock/object.h b/security/landlock/object.h
[...]
> +struct landlock_object {
> + /**
> + * @usage: This counter is used to tie an object to the rules matching
> + * it or to keep it alive while adding a new rule. If this counter
> + * reaches zero, this struct must not be modified, but this counter can
> + * still be read from within an RCU read-side critical section. When
> + * adding a new rule to an object with a usage counter of zero, we must
> + * wait until the pointer to this object is set to NULL (or recycled).
> + */
> + refcount_t usage;
> + /**
> + * @lock: Guards against concurrent modifications. This lock must be
s/must be/must 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;
[...]
> +};
> +
> +struct landlock_object *landlock_create_object(
> + const struct landlock_object_underops *const underops,
> + void *const underojb);
nit: "underobj"
next prev parent reply other threads:[~2020-10-29 1:07 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-27 20:03 [PATCH v22 00/12] Landlock LSM Mickaël Salaün
2020-10-27 20:03 ` [PATCH v22 01/12] landlock: Add object management Mickaël Salaün
2020-10-29 1:05 ` Jann Horn [this message]
2020-10-29 9:30 ` Mickaël Salaün
2020-10-30 3:02 ` Jann Horn
2020-11-16 21:26 ` Pavel Machek
2020-11-16 21:36 ` Mickaël Salaün
2020-10-27 20:03 ` [PATCH v22 02/12] landlock: Add ruleset and domain management Mickaël Salaün
2020-10-29 1:05 ` Jann Horn
2020-10-29 9:35 ` Mickaël Salaün
2020-10-27 20:03 ` [PATCH v22 03/12] landlock: Set up the security framework and manage credentials Mickaël Salaün
2020-10-29 1:06 ` Jann Horn
2020-10-27 20:03 ` [PATCH v22 04/12] landlock: Add ptrace restrictions Mickaël Salaün
2020-10-29 1:06 ` Jann Horn
2020-10-27 20:03 ` [PATCH v22 05/12] LSM: Infrastructure management of the superblock Mickaël Salaün
2020-10-28 5:29 ` James Morris
2020-10-27 20:03 ` [PATCH v22 06/12] fs,security: Add sb_delete hook Mickaël Salaün
2020-10-28 5:30 ` James Morris
2020-10-29 1:06 ` Jann Horn
2020-10-27 20:03 ` [PATCH v22 07/12] landlock: Support filesystem access-control Mickaël Salaün
2020-10-29 1:06 ` Jann Horn
2020-10-29 10:47 ` Mickaël Salaün
2020-11-03 16:03 ` Mickaël Salaün
2020-10-27 20:03 ` [PATCH v22 08/12] landlock: Add syscall implementations Mickaël Salaün
2020-10-29 1:06 ` Jann Horn
2020-10-29 11:30 ` Mickaël Salaün
2020-10-30 3:07 ` Jann Horn
2020-10-30 12:41 ` Mickaël Salaün
2020-10-27 20:03 ` [PATCH v22 09/12] arch: Wire up Landlock syscalls Mickaël Salaün
2020-10-28 5:31 ` James Morris
2020-10-27 20:03 ` [PATCH v22 10/12] selftests/landlock: Add user space tests Mickaël Salaün
2020-10-27 20:03 ` [PATCH v22 11/12] samples/landlock: Add a sandbox manager example Mickaël Salaün
2020-10-27 20:03 ` [PATCH v22 12/12] landlock: Add user and kernel documentation Mickaël Salaün
2020-10-29 1:07 ` Jann Horn
2020-10-29 11:38 ` Mickaël Salaün
2020-10-29 1:05 ` [PATCH v22 00/12] Landlock LSM Jann Horn
2020-10-29 11:40 ` Mickaël Salaün
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