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 02/12] landlock: Add ruleset and domain management
Date: Thu, 29 Oct 2020 02:05:53 +0100 [thread overview]
Message-ID: <CAG48ez1j9KELLconr2RTmzt6j7QkY-wKC+8fn-rsG+wfxFJ=jg@mail.gmail.com> (raw)
In-Reply-To: <20201027200358.557003-3-mic@digikod.net>
On Tue, Oct 27, 2020 at 9:04 PM Mickaël Salaün <mic@digikod.net> wrote:
> A Landlock ruleset is mainly a red-black tree with Landlock rules as
> nodes. This enables quick update and lookup to match a requested access
> e.g., to a file. A ruleset is usable through a dedicated file
> descriptor (cf. following commit implementing syscalls) which enables a
> process to create and populate a ruleset with new rules.
>
> A domain is a ruleset tied to a set of processes. This group of rules
> defines the security policy enforced on these processes and their future
> children. A domain can transition to a new domain which is the
> intersection of all its constraints and those of a ruleset provided by
> the current process. This modification only impact the current process.
> This means that a process can only gain more constraints (i.e. lose
> accesses) over time.
>
> 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>
with some nits:
[...]
> +static struct landlock_ruleset *create_ruleset(void)
> +{
> + struct landlock_ruleset *new_ruleset;
> +
> + new_ruleset = kzalloc(sizeof(*new_ruleset), GFP_KERNEL_ACCOUNT);
> + if (!new_ruleset)
> + return ERR_PTR(-ENOMEM);
> + refcount_set(&new_ruleset->usage, 1);
> + mutex_init(&new_ruleset->lock);
> + /*
> + * root = RB_ROOT
This should probably be done explicitly, even though it's currently a
no-op, in case the implementation of RB_ROOT changes in the future.
> + * hierarchy = NULL
> + * nb_rules = 0
> + * nb_layers = 0
> + * fs_access_mask = 0
> + */
> + return new_ruleset;
> +}
[...]
> +/**
> + * landlock_insert_rule - Insert a rule in a ruleset
> + *
> + * @ruleset: The ruleset to be updated.
> + * @rule: Read-only payload to be inserted (not own by this function).
s/own/owned/
> + * @is_merge: If true, intersects access rights and updates the rule's layers
> + * (e.g. merge two rulesets), else do a union of access rights and
> + * keep the rule's layers (e.g. extend a ruleset)
> + *
> + * Assumptions:
> + *
> + * - An inserted rule cannot be removed.
> + * - The underlying kernel object must be held by the caller.
> + */
> +int landlock_insert_rule(struct landlock_ruleset *const ruleset,
> + struct landlock_rule *const rule, const bool is_merge)
[...]
> +static int merge_ruleset(struct landlock_ruleset *const dst,
> + struct landlock_ruleset *const src)
> +{
> + struct landlock_rule *walker_rule, *next_rule;
> + int err = 0;
> +
> + might_sleep();
> + if (!src)
> + return 0;
> + /* Only merge into a domain. */
> + if (WARN_ON_ONCE(!dst || !dst->hierarchy))
> + return -EFAULT;
> +
> + mutex_lock(&dst->lock);
> + mutex_lock_nested(&src->lock, 1);
Maybe add a comment like this above these two lines? "Ruleset locks
are ordered by time of ruleset creation; dst is newer than src."
Also, maybe s/1/SINGLE_DEPTH_NESTING/.
> + /*
> + * Makes a new layer, but only increments the number of layers after
> + * the rules are inserted.
> + */
> + if (dst->nb_layers == sizeof(walker_rule->layers) * BITS_PER_BYTE) {
> + err = -E2BIG;
> + goto out_unlock;
> + }
> + dst->fs_access_mask |= src->fs_access_mask;
> +
> + /* Merges the @src tree. */
> + rbtree_postorder_for_each_entry_safe(walker_rule, next_rule,
> + &src->root, node) {
> + err = landlock_insert_rule(dst, walker_rule, true);
> + if (err)
> + goto out_unlock;
> + }
> + dst->nb_layers++;
> +
> +out_unlock:
> + mutex_unlock(&src->lock);
> + mutex_unlock(&dst->lock);
> + return err;
> +}
[...]
> diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
[...]
> +struct landlock_rule {
> + /**
> + * @node: Node in the red-black tree.
s/the red-black tree/the ruleset's red-black tree/
> + */
> + struct rb_node node;
> + /**
> + * @object: Pointer to identify a kernel object (e.g. an inode). This
> + * is used as a key for this ruleset element. This pointer is set once
> + * and never modified. It always point to an allocated object because
s/point/points/
> + * each rule increment the refcount of there object.
s/increment/increments/
s/there/its/
> + */
> + struct landlock_object *object;
> + /**
> + * @layers: Bitfield to identify the layers which resulted to @access
> + * from different consecutive intersections.
> + */
> + u64 layers;
> + /**
> + * @access: Bitfield of allowed actions on the kernel object. They are
> + * relative to the object type (e.g. %LANDLOCK_ACTION_FS_READ). This
> + * may be the result of the merged access rights (boolean AND) from
> + * multiple layers referring to the same object.
> + */
> + u32 access;
> +};
> +
> +/**
> + * struct landlock_hierarchy - Node in a ruleset hierarchy
> + */
> +struct landlock_hierarchy {
> + /**
> + * @parent: Pointer to the parent node, or NULL if it is a root Lanlock
nit: Landlock
> + * domain.
> + */
> + struct landlock_hierarchy *parent;
> + /**
> + * @usage: Number of potential children domains plus their parent
> + * domain.
> + */
> + refcount_t usage;
> +};
> +
> +/**
> + * struct landlock_ruleset - Landlock ruleset
> + *
> + * This data structure must contains unique entries, be updatable, and quick to
s/contains/contain/
> + * match an object.
> + */
> +struct landlock_ruleset {
> + /**
> + * @root: Root of a red-black tree containing &struct landlock_rule
> + * nodes.
Maybe add: "Once the ruleset is installed on a process, this tree is
immutable until @usage reaches zero."
> + */
> + struct rb_root root;
> + /**
> + * @hierarchy: Enables hierarchy identification even when a parent
> + * domain vanishes. This is needed for the ptrace protection.
> + */
> + struct landlock_hierarchy *hierarchy;
> + union {
> + /**
> + * @work_free: Enables to free a ruleset within a lockless
> + * section. This is only used by
> + * landlock_put_ruleset_deferred() when @usage reaches zero.
> + * The fields @lock, @usage, @nb_layers, @nb_rules and
> + * @fs_access_mask are then unused.
> + */
> + struct work_struct work_free;
> + struct {
> + /**
> + * @lock: Guards against concurrent modifications of
> + * @root, if @usage is greater than zero.
> + */
> + struct mutex lock;
> + /**
> + * @usage: Number of processes (i.e. domains) or file
> + * descriptors referencing this ruleset.
> + */
> + refcount_t usage;
> + /**
> + * @nb_rules: Number of non-overlapping (i.e. not for
> + * the same object) rules in this ruleset.
> + */
> + u32 nb_rules;
> + /**
> + * @nb_layers: Number of layers which are used in this
> + * ruleset. This enables to check that all the layers
> + * allow an access request. A value of 0 identify a
s/identify/identifies/
> + * non-merged ruleset (i.e. not a domain).
> + */
> + u32 nb_layers;
> + /**
> + * @fs_access_mask: Contains the subset of filesystem
> + * actions which are restricted by a ruleset. This is
> + * used when merging rulesets and for user space
> + * backward compatibility (i.e. future-proof). Set
> + * once and never changed for the lifetime of the
> + * ruleset.
> + */
> + u32 fs_access_mask;
> + };
> + };
> +};
next prev parent reply other threads:[~2020-10-29 1:06 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
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 [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAG48ez1j9KELLconr2RTmzt6j7QkY-wKC+8fn-rsG+wfxFJ=jg@mail.gmail.com' \
--to=jannh@google.com \
--cc=anton.ivanov@cambridgegreys.com \
--cc=arnd@arndb.de \
--cc=casey@schaufler-ca.com \
--cc=corbet@lwn.net \
--cc=jdike@addtoit.com \
--cc=jmorris@namei.org \
--cc=keescook@chromium.org \
--cc=kernel-hardening@lists.openwall.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=luto@amacapital.net \
--cc=mic@digikod.net \
--cc=mic@linux.microsoft.com \
--cc=mtk.manpages@gmail.com \
--cc=richard@nod.at \
--cc=serge@hallyn.com \
--cc=shuah@kernel.org \
--cc=vincent.dagonneau@ssi.gouv.fr \
--cc=viro@zeniv.linux.org.uk \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).