[PATCH v7 08/18] landlock: add network rules support

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This commit adds network rules support in internal landlock functions
(presented in ruleset.c) and landlock_create_ruleset syscall.

Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@xxxxxxxxxx>
---

Changes since v6:
* Renames landlock_set_net_access_mask() to landlock_add_net_access_mask()
  because it OR values.
* Makes landlock_add_net_access_mask() more resilient incorrect values.
* Refactors landlock_get_net_access_mask().
* Renames LANDLOCK_MASK_SHIFT_NET to LANDLOCK_SHIFT_ACCESS_NET and use
  LANDLOCK_NUM_ACCESS_FS as value.
* Updates access_masks_t to u32 to support network access actions.
* Refactors landlock internal functions to support network actions with
  landlock_key/key_type/id types.

Changes since v5:
* Gets rid of partial revert from landlock_add_rule
syscall.
* Formats code with clang-format-14.

Changes since v4:
* Refactors landlock_create_ruleset() - splits ruleset and
masks checks.
* Refactors landlock_create_ruleset() and landlock mask
setters/getters to support two rule types.
* Refactors landlock_add_rule syscall add_rule_path_beneath
function by factoring out get_ruleset_from_fd() and
landlock_put_ruleset().

Changes since v3:
* Splits commit.
* Adds network rule support for internal landlock functions.
* Adds set_mask and get_mask for network.
* Adds rb_root root_net_port.

---
 security/landlock/limits.h   |  6 +++++-
 security/landlock/ruleset.c  | 38 +++++++++++++++++++++++++++++----
 security/landlock/ruleset.h  | 41 ++++++++++++++++++++++++++++++++++--
 security/landlock/syscalls.c |  8 ++++++-
 4 files changed, 85 insertions(+), 8 deletions(-)

diff --git a/security/landlock/limits.h b/security/landlock/limits.h
index bafb3b8dc677..8a1a6463c64e 100644
--- a/security/landlock/limits.h
+++ b/security/landlock/limits.h
@@ -23,6 +23,10 @@
 #define LANDLOCK_NUM_ACCESS_FS		__const_hweight64(LANDLOCK_MASK_ACCESS_FS)
 #define LANDLOCK_SHIFT_ACCESS_FS	0

-/* clang-format on */
+#define LANDLOCK_LAST_ACCESS_NET	LANDLOCK_ACCESS_NET_CONNECT_TCP
+#define LANDLOCK_MASK_ACCESS_NET	((LANDLOCK_LAST_ACCESS_NET << 1) - 1)
+#define LANDLOCK_NUM_ACCESS_NET		__const_hweight64(LANDLOCK_MASK_ACCESS_NET)
+#define LANDLOCK_SHIFT_ACCESS_NET	LANDLOCK_NUM_ACCESS_FS

+/* clang-format on */
 #endif /* _SECURITY_LANDLOCK_LIMITS_H */
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index 84fcd8eb30d4..442f212039df 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -36,6 +36,7 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
 	refcount_set(&new_ruleset->usage, 1);
 	mutex_init(&new_ruleset->lock);
 	new_ruleset->root_inode = RB_ROOT;
+	new_ruleset->root_net_port = RB_ROOT;
 	new_ruleset->num_layers = num_layers;
 	/*
 	 * hierarchy = NULL
@@ -46,16 +47,21 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
 }

 struct landlock_ruleset *
-landlock_create_ruleset(const access_mask_t fs_access_mask)
+landlock_create_ruleset(const access_mask_t fs_access_mask,
+			const access_mask_t net_access_mask)
 {
 	struct landlock_ruleset *new_ruleset;

 	/* Informs about useless ruleset. */
-	if (!fs_access_mask)
+	if (!fs_access_mask && !net_access_mask)
 		return ERR_PTR(-ENOMSG);
 	new_ruleset = create_ruleset(1);
-	if (!IS_ERR(new_ruleset))
+	if (IS_ERR(new_ruleset))
+		return new_ruleset;
+	if (fs_access_mask)
 		landlock_add_fs_access_mask(new_ruleset, fs_access_mask, 0);
+	if (net_access_mask)
+		landlock_add_net_access_mask(new_ruleset, net_access_mask, 0);
 	return new_ruleset;
 }

@@ -73,6 +79,8 @@ static inline bool is_object_pointer(const enum landlock_key_type key_type)
 	switch (key_type) {
 	case LANDLOCK_KEY_INODE:
 		return true;
+	case LANDLOCK_KEY_NET_PORT:
+		return false;
 	}
 	WARN_ON_ONCE(1);
 	return false;
@@ -126,6 +134,9 @@ static inline struct rb_root *get_root(struct landlock_ruleset *const ruleset,
 	case LANDLOCK_KEY_INODE:
 		root = &ruleset->root_inode;
 		break;
+	case LANDLOCK_KEY_NET_PORT:
+		root = &ruleset->root_net_port;
+		break;
 	}
 	if (WARN_ON_ONCE(!root))
 		return ERR_PTR(-EINVAL);
@@ -154,7 +165,9 @@ static void build_check_ruleset(void)
 	BUILD_BUG_ON(ruleset.num_rules < LANDLOCK_MAX_NUM_RULES);
 	BUILD_BUG_ON(ruleset.num_layers < LANDLOCK_MAX_NUM_LAYERS);
 	BUILD_BUG_ON(access_masks <
-		     (LANDLOCK_MASK_ACCESS_FS << LANDLOCK_SHIFT_ACCESS_FS));
+		     (LANDLOCK_MASK_ACCESS_FS << LANDLOCK_SHIFT_ACCESS_FS) +
+			     (LANDLOCK_MASK_ACCESS_NET
+			      << LANDLOCK_SHIFT_ACCESS_NET));
 }

 /**
@@ -367,6 +380,11 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
 	if (err)
 		goto out_unlock;

+	/* Merges the @src network port tree. */
+	err = merge_tree(dst, src, LANDLOCK_KEY_NET_PORT);
+	if (err)
+		goto out_unlock;
+
 out_unlock:
 	mutex_unlock(&src->lock);
 	mutex_unlock(&dst->lock);
@@ -419,6 +437,11 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
 	if (err)
 		goto out_unlock;

+	/* Copies the @parent network port tree. */
+	err = inherit_tree(parent, child, LANDLOCK_KEY_NET_PORT);
+	if (err)
+		goto out_unlock;
+
 	if (WARN_ON_ONCE(child->num_layers <= parent->num_layers)) {
 		err = -EINVAL;
 		goto out_unlock;
@@ -451,6 +474,9 @@ static void free_ruleset(struct landlock_ruleset *const ruleset)
 	rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root_inode,
 					     node)
 		free_rule(freeme, LANDLOCK_KEY_INODE);
+	rbtree_postorder_for_each_entry_safe(freeme, next,
+					     &ruleset->root_net_port, node)
+		free_rule(freeme, LANDLOCK_KEY_NET_PORT);
 	put_hierarchy(ruleset->hierarchy);
 	kfree(ruleset);
 }
@@ -640,6 +666,10 @@ access_mask_t init_layer_masks(const struct landlock_ruleset *const domain,
 		get_access_mask = landlock_get_fs_access_mask;
 		num_access = LANDLOCK_NUM_ACCESS_FS;
 		break;
+	case LANDLOCK_KEY_NET_PORT:
+		get_access_mask = landlock_get_net_access_mask;
+		num_access = LANDLOCK_NUM_ACCESS_NET;
+		break;
 	default:
 		WARN_ON_ONCE(1);
 		return 0;
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index 2083855bf42d..d456ee90b648 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -26,7 +26,7 @@ static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS);
 static_assert(sizeof(unsigned long) >= sizeof(access_mask_t));

 /* Ruleset access masks. */
-typedef u16 access_masks_t;
+typedef u32 access_masks_t;
 /* Makes sure all ruleset access rights can be stored. */
 static_assert(BITS_PER_TYPE(access_masks_t) >= LANDLOCK_NUM_ACCESS_FS);

@@ -66,6 +66,11 @@ enum landlock_key_type {
 	 * keys.
 	 */
 	LANDLOCK_KEY_INODE = 1,
+	/**
+	 * @LANDLOCK_KEY_NET_PORT: Type of &landlock_ruleset.root_net_port's
+	 * node keys.
+	 */
+	LANDLOCK_KEY_NET_PORT = 2,
 };

 /**
@@ -133,6 +138,12 @@ struct landlock_ruleset {
 	 * reaches zero.
 	 */
 	struct rb_root root_inode;
+	/**
+	 * @root_net_port: Root of a red-black tree containing object nodes
+	 * for network port. Once a ruleset is tied to a process (i.e. as a domain),
+	 * this tree is immutable until @usage reaches zero.
+	 */
+	struct rb_root root_net_port;
 	/**
 	 * @hierarchy: Enables hierarchy identification even when a parent
 	 * domain vanishes.  This is needed for the ptrace protection.
@@ -188,7 +199,8 @@ struct landlock_ruleset {
 };

 struct landlock_ruleset *
-landlock_create_ruleset(const access_mask_t access_mask);
+landlock_create_ruleset(const access_mask_t access_mask_fs,
+			const access_mask_t access_mask_net);

 void landlock_put_ruleset(struct landlock_ruleset *const ruleset);
 void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset);
@@ -226,6 +238,21 @@ landlock_add_fs_access_mask(struct landlock_ruleset *const ruleset,
 		(fs_mask << LANDLOCK_SHIFT_ACCESS_FS);
 }

+/* A helper function to set a network mask. */
+static inline void
+landlock_add_net_access_mask(struct landlock_ruleset *const ruleset,
+			     const access_mask_t net_access_mask,
+			     const u16 layer_level)
+{
+	access_mask_t net_mask = net_access_mask & LANDLOCK_MASK_ACCESS_NET;
+
+	/* Should already be checked in sys_landlock_create_ruleset(). */
+	WARN_ON_ONCE(net_access_mask != net_mask);
+	// TODO: Add tests to check "|=" and not "="
+	ruleset->access_masks[layer_level] |=
+		(net_mask << LANDLOCK_SHIFT_ACCESS_NET);
+}
+
 /* A helper function to get a filesystem mask. */
 static inline access_mask_t
 landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
@@ -236,6 +263,16 @@ landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
 	       LANDLOCK_MASK_ACCESS_FS;
 }

+/* A helper function to get a network mask. */
+static inline access_mask_t
+landlock_get_net_access_mask(const struct landlock_ruleset *const ruleset,
+			     const u16 layer_level)
+{
+	return (ruleset->access_masks[layer_level] >>
+		LANDLOCK_SHIFT_ACCESS_NET) &
+	       LANDLOCK_MASK_ACCESS_NET;
+}
+
 bool unmask_layers(const struct landlock_rule *const rule,
 		   const access_mask_t access_request,
 		   layer_mask_t (*const layer_masks)[],
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index ffd5805eddd9..641155f6f6f8 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -189,8 +189,14 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
 	    LANDLOCK_MASK_ACCESS_FS)
 		return -EINVAL;

+	/* Checks network content (and 32-bits cast). */
+	if ((ruleset_attr.handled_access_net | LANDLOCK_MASK_ACCESS_NET) !=
+	    LANDLOCK_MASK_ACCESS_NET)
+		return -EINVAL;
+
 	/* Checks arguments and transforms to kernel struct. */
-	ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs);
+	ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs,
+					  ruleset_attr.handled_access_net);
 	if (IS_ERR(ruleset))
 		return PTR_ERR(ruleset);

--
2.25.1




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