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Date:   Fri, 21 Oct 2022 23:26:37 +0800
From:   Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
To:     <mic@...ikod.net>
CC:     <willemdebruijn.kernel@...il.com>, <gnoack3000@...il.com>,
        <linux-security-module@...r.kernel.org>, <netdev@...r.kernel.org>,
        <netfilter-devel@...r.kernel.org>, <artem.kuzin@...wei.com>
Subject: [PATCH v8 05/12] landlock: Refactor unmask_layers() and init_layer_masks()

Adds new key_type argument to init_layer_masks() helper.
Adds masks_array_size argument  to unmask_layers() helper.
These modifications support implementing new rule types in the next
Landlock versions.

Co-developed-by: Mickaël Salaün <mic@...ikod.net>
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
---

Changes since v7:
* Refactors commit message, adds a co-developer.
* Minor fixes.

Changes since v6:
* Removes masks_size attribute from init_layer_masks().
* Refactors init_layer_masks() with new landlock_key_type.

Changes since v5:
* Splits commit.
* Formats code with clang-format-14.

Changes since v4:
* Refactors init_layer_masks(), get_handled_accesses()
and unmask_layers() functions to support multiple rule types.
* Refactors landlock_get_fs_access_mask() function with
LANDLOCK_MASK_ACCESS_FS mask.

Changes since v3:
* Splits commit.
* Refactors landlock_unmask_layers functions.

---
 security/landlock/fs.c      | 36 ++++++++++++++++++-------------
 security/landlock/ruleset.c | 42 ++++++++++++++++++++++++++-----------
 security/landlock/ruleset.h | 11 +++++-----
 3 files changed, 58 insertions(+), 31 deletions(-)

diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 240e42a8f788..fe76a11483f8 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -435,16 +435,20 @@ static bool is_access_to_paths_allowed(
 	if (unlikely(dentry_child1)) {
 		unmask_layers(find_rule(domain, dentry_child1),
 			      init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
-					       &_layer_masks_child1),
-			      &_layer_masks_child1);
+					       &_layer_masks_child1,
+					       LANDLOCK_KEY_INODE),
+			      &_layer_masks_child1,
+			      ARRAY_SIZE(_layer_masks_child1));
 		layer_masks_child1 = &_layer_masks_child1;
 		child1_is_directory = d_is_dir(dentry_child1);
 	}
 	if (unlikely(dentry_child2)) {
 		unmask_layers(find_rule(domain, dentry_child2),
 			      init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
-					       &_layer_masks_child2),
-			      &_layer_masks_child2);
+					       &_layer_masks_child2,
+					       LANDLOCK_KEY_INODE),
+			      &_layer_masks_child2,
+			      ARRAY_SIZE(_layer_masks_child2));
 		layer_masks_child2 = &_layer_masks_child2;
 		child2_is_directory = d_is_dir(dentry_child2);
 	}
@@ -496,15 +500,16 @@ static bool is_access_to_paths_allowed(
 		}

 		rule = find_rule(domain, walker_path.dentry);
-		allowed_parent1 = unmask_layers(rule, access_masked_parent1,
-						layer_masks_parent1);
-		allowed_parent2 = unmask_layers(rule, access_masked_parent2,
-						layer_masks_parent2);
+		allowed_parent1 = unmask_layers(
+			rule, access_masked_parent1, layer_masks_parent1,
+			ARRAY_SIZE(*layer_masks_parent1));
+		allowed_parent2 = unmask_layers(
+			rule, access_masked_parent2, layer_masks_parent2,
+			ARRAY_SIZE(*layer_masks_parent2));

 		/* Stops when a rule from each layer grants access. */
 		if (allowed_parent1 && allowed_parent2)
 			break;
-
 jump_up:
 		if (walker_path.dentry == walker_path.mnt->mnt_root) {
 			if (follow_up(&walker_path)) {
@@ -543,7 +548,8 @@ static inline int check_access_path(const struct landlock_ruleset *const domain,
 {
 	layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {};

-	access_request = init_layer_masks(domain, access_request, &layer_masks);
+	access_request = init_layer_masks(domain, access_request, &layer_masks,
+					  LANDLOCK_KEY_INODE);
 	if (is_access_to_paths_allowed(domain, path, access_request,
 				       &layer_masks, NULL, 0, NULL, NULL))
 		return 0;
@@ -630,7 +636,7 @@ static bool collect_domain_accesses(
 		return true;

 	access_dom = init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
-				      layer_masks_dom);
+				      layer_masks_dom, LANDLOCK_KEY_INODE);

 	dget(dir);
 	while (true) {
@@ -638,7 +644,8 @@ static bool collect_domain_accesses(

 		/* Gets all layers allowing all domain accesses. */
 		if (unmask_layers(find_rule(domain, dir), access_dom,
-				  layer_masks_dom)) {
+				  layer_masks_dom,
+				  ARRAY_SIZE(*layer_masks_dom))) {
 			/*
 			 * Stops when all handled accesses are allowed by at
 			 * least one rule in each layer.
@@ -754,7 +761,7 @@ static int current_check_refer_path(struct dentry *const old_dentry,
 		 */
 		access_request_parent1 = init_layer_masks(
 			dom, access_request_parent1 | access_request_parent2,
-			&layer_masks_parent1);
+			&layer_masks_parent1, LANDLOCK_KEY_INODE);
 		if (is_access_to_paths_allowed(
 			    dom, new_dir, access_request_parent1,
 			    &layer_masks_parent1, NULL, 0, NULL, NULL))
@@ -1131,7 +1138,8 @@ static int hook_file_open(struct file *const file)

 	if (is_access_to_paths_allowed(
 		    dom, &file->f_path,
-		    init_layer_masks(dom, full_access_request, &layer_masks),
+		    init_layer_masks(dom, full_access_request, &layer_masks,
+				     LANDLOCK_KEY_INODE),
 		    &layer_masks, NULL, 0, NULL, NULL)) {
 		allowed_access = full_access_request;
 	} else {
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index 02ab14439c43..c7cf54ba4f6d 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -576,13 +576,15 @@ landlock_find_rule(const struct landlock_ruleset *const ruleset,
 /*
  * @layer_masks is read and may be updated according to the access request and
  * the matching rule.
+ * @masks_array_size must be equal to ARRAY_SIZE(*layer_masks).
  *
  * Returns true if the request is allowed (i.e. relevant layer masks for the
  * request are empty).
  */
 bool unmask_layers(const struct landlock_rule *const rule,
 		   const access_mask_t access_request,
-		   layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
+		   layer_mask_t (*const layer_masks)[],
+		   const size_t masks_array_size)
 {
 	size_t layer_level;

@@ -614,8 +616,7 @@ bool unmask_layers(const struct landlock_rule *const rule,
 		 * requested access.
 		 */
 		is_empty = true;
-		for_each_set_bit(access_bit, &access_req,
-				 ARRAY_SIZE(*layer_masks)) {
+		for_each_set_bit(access_bit, &access_req, masks_array_size) {
 			if (layer->access & BIT_ULL(access_bit))
 				(*layer_masks)[access_bit] &= ~layer_bit;
 			is_empty = is_empty && !(*layer_masks)[access_bit];
@@ -626,6 +627,10 @@ bool unmask_layers(const struct landlock_rule *const rule,
 	return false;
 }

+typedef access_mask_t
+get_access_mask_t(const struct landlock_ruleset *const ruleset,
+		  const u16 layer_level);
+
 /**
  * init_layer_masks - Initialize layer masks from an access request
  *
@@ -635,19 +640,33 @@ bool unmask_layers(const struct landlock_rule *const rule,
  * @domain: The domain that defines the current restrictions.
  * @access_request: The requested access rights to check.
  * @layer_masks: The layer masks to populate.
+ * @key_type: The key type to switch between access masks of different types.
  *
  * Returns: An access mask where each access right bit is set which is handled
  * in any of the active layers in @domain.
  */
-access_mask_t
-init_layer_masks(const struct landlock_ruleset *const domain,
-		 const access_mask_t access_request,
-		 layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
+access_mask_t init_layer_masks(const struct landlock_ruleset *const domain,
+			       const access_mask_t access_request,
+			       layer_mask_t (*const layer_masks)[],
+			       const enum landlock_key_type key_type)
 {
 	access_mask_t handled_accesses = 0;
-	size_t layer_level;
+	size_t layer_level, num_access;
+	get_access_mask_t *get_access_mask;
+
+	switch (key_type) {
+	case LANDLOCK_KEY_INODE:
+		get_access_mask = landlock_get_fs_access_mask;
+		num_access = LANDLOCK_NUM_ACCESS_FS;
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		return 0;
+	}
+
+	memset(layer_masks, 0,
+	       array_size(sizeof((*layer_masks)[0]), num_access));

-	memset(layer_masks, 0, sizeof(*layer_masks));
 	/* An empty access request can happen because of O_WRONLY | O_RDWR. */
 	if (!access_request)
 		return 0;
@@ -657,14 +676,13 @@ init_layer_masks(const struct landlock_ruleset *const domain,
 		const unsigned long access_req = access_request;
 		unsigned long access_bit;

-		for_each_set_bit(access_bit, &access_req,
-				 ARRAY_SIZE(*layer_masks)) {
+		for_each_set_bit(access_bit, &access_req, num_access) {
 			/*
 			 * Artificially handles all initially denied by default
 			 * access rights.
 			 */
 			if (BIT_ULL(access_bit) &
-			    (landlock_get_fs_access_mask(domain, layer_level) |
+			    (get_access_mask(domain, layer_level) |
 			     ACCESS_INITIALLY_DENIED)) {
 				(*layer_masks)[access_bit] |=
 					BIT_ULL(layer_level);
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index 50baff4fcbb4..d9eb79ea9a89 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -259,11 +259,12 @@ landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,

 bool unmask_layers(const struct landlock_rule *const rule,
 		   const access_mask_t access_request,
-		   layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS]);
+		   layer_mask_t (*const layer_masks)[],
+		   const size_t masks_array_size);

-access_mask_t
-init_layer_masks(const struct landlock_ruleset *const domain,
-		 const access_mask_t access_request,
-		 layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS]);
+access_mask_t init_layer_masks(const struct landlock_ruleset *const domain,
+			       const access_mask_t access_request,
+			       layer_mask_t (*const layer_masks)[],
+			       const enum landlock_key_type key_type);

 #endif /* _SECURITY_LANDLOCK_RULESET_H */
--
2.25.1

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