Merge tag 'landlock-5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux

Pull Landlock updates from Mickaël Salaün:

 - improve the path_rename LSM hook implementations for RENAME_EXCHANGE;

 - fix a too-restrictive filesystem control for a rare corner case;

 - set the nested sandbox limitation to 16 layers;

 - add a new LANDLOCK_ACCESS_FS_REFER access right to properly handle
   file reparenting (i.e. full rename and link support);

 - add new tests and documentation;

 - format code with clang-format to make it easier to maintain and
   contribute.

* tag 'landlock-5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux: (30 commits)
  landlock: Explain how to support Landlock
  landlock: Add design choices documentation for filesystem access rights
  landlock: Document good practices about filesystem policies
  landlock: Document LANDLOCK_ACCESS_FS_REFER and ABI versioning
  samples/landlock: Add support for file reparenting
  selftests/landlock: Add 11 new test suites dedicated to file reparenting
  landlock: Add support for file reparenting with LANDLOCK_ACCESS_FS_REFER
  LSM: Remove double path_rename hook calls for RENAME_EXCHANGE
  landlock: Move filesystem helpers and add a new one
  landlock: Fix same-layer rule unions
  landlock: Create find_rule() from unmask_layers()
  landlock: Reduce the maximum number of layers to 16
  landlock: Define access_mask_t to enforce a consistent access mask size
  selftests/landlock: Test landlock_create_ruleset(2) argument check ordering
  landlock: Change landlock_restrict_self(2) check ordering
  landlock: Change landlock_add_rule(2) argument check ordering
  selftests/landlock: Add tests for O_PATH
  selftests/landlock: Fully test file rename with "remove" access
  selftests/landlock: Extend access right tests to directories
  selftests/landlock: Add tests for unknown access rights
  ...

14 files changed, 848 insertions, 286 deletions

diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 4f0eecb67dde..900bc540656a 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -354,13 +354,16 @@ static int apparmor_path_link(struct dentry *old_dentry, const struct path *new_
 }
 
 static int apparmor_path_rename(const struct path *old_dir, struct dentry *old_dentry,
-				const struct path *new_dir, struct dentry *new_dentry)
+				const struct path *new_dir, struct dentry *new_dentry,
+				const unsigned int flags)
 {
 	struct aa_label *label;
 	int error = 0;
 
 	if (!path_mediated_fs(old_dentry))
 		return 0;
+	if ((flags & RENAME_EXCHANGE) && !path_mediated_fs(new_dentry))
+		return 0;
 
 	label = begin_current_label_crit_section();
 	if (!unconfined(label)) {
@@ -374,10 +377,27 @@ static int apparmor_path_rename(const struct path *old_dir, struct dentry *old_d
 			d_backing_inode(old_dentry)->i_mode
 		};
 
-		error = aa_path_perm(OP_RENAME_SRC, label, &old_path, 0,
-				     MAY_READ | AA_MAY_GETATTR | MAY_WRITE |
-				     AA_MAY_SETATTR | AA_MAY_DELETE,
-				     &cond);
+		if (flags & RENAME_EXCHANGE) {
+			struct path_cond cond_exchange = {
+				i_uid_into_mnt(mnt_userns, d_backing_inode(new_dentry)),
+				d_backing_inode(new_dentry)->i_mode
+			};
+
+			error = aa_path_perm(OP_RENAME_SRC, label, &new_path, 0,
+					     MAY_READ | AA_MAY_GETATTR | MAY_WRITE |
+					     AA_MAY_SETATTR | AA_MAY_DELETE,
+					     &cond_exchange);
+			if (!error)
+				error = aa_path_perm(OP_RENAME_DEST, label, &old_path,
+						     0, MAY_WRITE | AA_MAY_SETATTR |
+						     AA_MAY_CREATE, &cond_exchange);
+		}
+
+		if (!error)
+			error = aa_path_perm(OP_RENAME_SRC, label, &old_path, 0,
+					     MAY_READ | AA_MAY_GETATTR | MAY_WRITE |
+					     AA_MAY_SETATTR | AA_MAY_DELETE,
+					     &cond);
 		if (!error)
 			error = aa_path_perm(OP_RENAME_DEST, label, &new_path,
 					     0, MAY_WRITE | AA_MAY_SETATTR |
diff --git a/security/landlock/cred.c b/security/landlock/cred.c
index 6725af24c684..ec6c37f04a19 100644
--- a/security/landlock/cred.c
+++ b/security/landlock/cred.c
@@ -15,7 +15,7 @@
 #include "setup.h"
 
 static int hook_cred_prepare(struct cred *const new,
-		const struct cred *const old, const gfp_t gfp)
+			     const struct cred *const old, const gfp_t gfp)
 {
 	struct landlock_ruleset *const old_dom = landlock_cred(old)->domain;
 
@@ -42,5 +42,5 @@ static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = {
 __init void landlock_add_cred_hooks(void)
 {
 	security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
-			LANDLOCK_NAME);
+			   LANDLOCK_NAME);
 }
diff --git a/security/landlock/cred.h b/security/landlock/cred.h
index 5f99d3decade..af89ab00e6d1 100644
--- a/security/landlock/cred.h
+++ b/security/landlock/cred.h
@@ -20,8 +20,8 @@ struct landlock_cred_security {
 	struct landlock_ruleset *domain;
 };
 
-static inline struct landlock_cred_security *landlock_cred(
-		const struct cred *cred)
+static inline struct landlock_cred_security *
+landlock_cred(const struct cred *cred)
 {
 	return cred->security + landlock_blob_sizes.lbs_cred;
 }
@@ -34,8 +34,8 @@ static inline const struct landlock_ruleset *landlock_get_current_domain(void)
 /*
  * The call needs to come from an RCU read-side critical section.
  */
-static inline const struct landlock_ruleset *landlock_get_task_domain(
-		const struct task_struct *const task)
+static inline const struct landlock_ruleset *
+landlock_get_task_domain(const struct task_struct *const task)
 {
 	return landlock_cred(__task_cred(task))->domain;
 }
diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 97b8e421f617..ec5a6247cd3e 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -4,6 +4,7 @@
  *
  * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
  * Copyright © 2018-2020 ANSSI
+ * Copyright © 2021-2022 Microsoft Corporation
  */
 
 #include <linux/atomic.h>
@@ -141,23 +142,26 @@ retry:
 }
 
 /* All access rights that can be tied to files. */
+/* clang-format off */
 #define ACCESS_FILE ( \
 	LANDLOCK_ACCESS_FS_EXECUTE | \
 	LANDLOCK_ACCESS_FS_WRITE_FILE | \
 	LANDLOCK_ACCESS_FS_READ_FILE)
+/* clang-format on */
 
 /*
  * @path: Should have been checked by get_path_from_fd().
  */
 int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
-		const struct path *const path, u32 access_rights)
+			    const struct path *const path,
+			    access_mask_t access_rights)
 {
 	int err;
 	struct landlock_object *object;
 
 	/* Files only get access rights that make sense. */
-	if (!d_is_dir(path->dentry) && (access_rights | ACCESS_FILE) !=
-			ACCESS_FILE)
+	if (!d_is_dir(path->dentry) &&
+	    (access_rights | ACCESS_FILE) != ACCESS_FILE)
 		return -EINVAL;
 	if (WARN_ON_ONCE(ruleset->num_layers != 1))
 		return -EINVAL;
@@ -180,84 +184,352 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
 
 /* Access-control management */
 
-static inline u64 unmask_layers(
-		const struct landlock_ruleset *const domain,
-		const struct path *const path, const u32 access_request,
-		u64 layer_mask)
+/*
+ * The lifetime of the returned rule is tied to @domain.
+ *
+ * Returns NULL if no rule is found or if @dentry is negative.
+ */
+static inline const struct landlock_rule *
+find_rule(const struct landlock_ruleset *const domain,
+	  const struct dentry *const dentry)
 {
 	const struct landlock_rule *rule;
 	const struct inode *inode;
-	size_t i;
 
-	if (d_is_negative(path->dentry))
-		/* Ignore nonexistent leafs. */
-		return layer_mask;
-	inode = d_backing_inode(path->dentry);
+	/* Ignores nonexistent leafs. */
+	if (d_is_negative(dentry))
+		return NULL;
+
+	inode = d_backing_inode(dentry);
 	rcu_read_lock();
-	rule = landlock_find_rule(domain,
-			rcu_dereference(landlock_inode(inode)->object));
+	rule = landlock_find_rule(
+		domain, rcu_dereference(landlock_inode(inode)->object));
 	rcu_read_unlock();
+	return rule;
+}
+
+/*
+ * @layer_masks is read and may be updated according to the access request and
+ * the matching rule.
+ *
+ * Returns true if the request is allowed (i.e. relevant layer masks for the
+ * request are empty).
+ */
+static inline 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])
+{
+	size_t layer_level;
+
+	if (!access_request || !layer_masks)
+		return true;
 	if (!rule)
-		return layer_mask;
+		return false;
 
 	/*
 	 * An access is granted if, for each policy layer, at least one rule
-	 * encountered on the pathwalk grants the requested accesses,
-	 * regardless of their position in the layer stack.  We must then check
+	 * encountered on the pathwalk grants the requested access,
+	 * regardless of its position in the layer stack.  We must then check
 	 * the remaining layers for each inode, from the first added layer to
-	 * the last one.
+	 * the last one.  When there is multiple requested accesses, for each
+	 * policy layer, the full set of requested accesses may not be granted
+	 * by only one rule, but by the union (binary OR) of multiple rules.
+	 * E.g. /a/b <execute> + /a <read> => /a/b <execute + read>
 	 */
-	for (i = 0; i < rule->num_layers; i++) {
-		const struct landlock_layer *const layer = &rule->layers[i];
-		const u64 layer_level = BIT_ULL(layer->level - 1);
+	for (layer_level = 0; layer_level < rule->num_layers; layer_level++) {
+		const struct landlock_layer *const layer =
+			&rule->layers[layer_level];
+		const layer_mask_t layer_bit = BIT_ULL(layer->level - 1);
+		const unsigned long access_req = access_request;
+		unsigned long access_bit;
+		bool is_empty;
 
-		/* Checks that the layer grants access to the full request. */
-		if ((layer->access & access_request) == access_request) {
-			layer_mask &= ~layer_level;
-
-			if (layer_mask == 0)
-				return layer_mask;
+		/*
+		 * Records in @layer_masks which layer grants access to each
+		 * requested access.
+		 */
+		is_empty = true;
+		for_each_set_bit(access_bit, &access_req,
+				 ARRAY_SIZE(*layer_masks)) {
+			if (layer->access & BIT_ULL(access_bit))
+				(*layer_masks)[access_bit] &= ~layer_bit;
+			is_empty = is_empty && !(*layer_masks)[access_bit];
 		}
+		if (is_empty)
+			return true;
 	}
-	return layer_mask;
+	return false;
 }
 
-static int check_access_path(const struct landlock_ruleset *const domain,
-		const struct path *const path, u32 access_request)
+/*
+ * Allows access to pseudo filesystems that will never be mountable (e.g.
+ * sockfs, pipefs), but can still be reachable through
+ * /proc/<pid>/fd/<file-descriptor>
+ */
+static inline bool is_nouser_or_private(const struct dentry *dentry)
 {
-	bool allowed = false;
-	struct path walker_path;
-	u64 layer_mask;
-	size_t i;
+	return (dentry->d_sb->s_flags & SB_NOUSER) ||
+	       (d_is_positive(dentry) &&
+		unlikely(IS_PRIVATE(d_backing_inode(dentry))));
+}
 
-	/* Make sure all layers can be checked. */
-	BUILD_BUG_ON(BITS_PER_TYPE(layer_mask) < LANDLOCK_MAX_NUM_LAYERS);
+static inline access_mask_t
+get_handled_accesses(const struct landlock_ruleset *const domain)
+{
+	access_mask_t access_dom = 0;
+	unsigned long access_bit;
+
+	for (access_bit = 0; access_bit < LANDLOCK_NUM_ACCESS_FS;
+	     access_bit++) {
+		size_t layer_level;
+
+		for (layer_level = 0; layer_level < domain->num_layers;
+		     layer_level++) {
+			if (domain->fs_access_masks[layer_level] &
+			    BIT_ULL(access_bit)) {
+				access_dom |= BIT_ULL(access_bit);
+				break;
+			}
+		}
+	}
+	return access_dom;
+}
+
+static inline 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 handled_accesses = 0;
+	size_t layer_level;
 
+	memset(layer_masks, 0, sizeof(*layer_masks));
+	/* An empty access request can happen because of O_WRONLY | O_RDWR. */
 	if (!access_request)
 		return 0;
+
+	/* Saves all handled accesses per layer. */
+	for (layer_level = 0; layer_level < domain->num_layers; layer_level++) {
+		const unsigned long access_req = access_request;
+		unsigned long access_bit;
+
+		for_each_set_bit(access_bit, &access_req,
+				 ARRAY_SIZE(*layer_masks)) {
+			if (domain->fs_access_masks[layer_level] &
+			    BIT_ULL(access_bit)) {
+				(*layer_masks)[access_bit] |=
+					BIT_ULL(layer_level);
+				handled_accesses |= BIT_ULL(access_bit);
+			}
+		}
+	}
+	return handled_accesses;
+}
+
+/*
+ * Check that a destination file hierarchy has more restrictions than a source
+ * file hierarchy.  This is only used for link and rename actions.
+ *
+ * @layer_masks_child2: Optional child masks.
+ */
+static inline bool no_more_access(
+	const layer_mask_t (*const layer_masks_parent1)[LANDLOCK_NUM_ACCESS_FS],
+	const layer_mask_t (*const layer_masks_child1)[LANDLOCK_NUM_ACCESS_FS],
+	const bool child1_is_directory,
+	const layer_mask_t (*const layer_masks_parent2)[LANDLOCK_NUM_ACCESS_FS],
+	const layer_mask_t (*const layer_masks_child2)[LANDLOCK_NUM_ACCESS_FS],
+	const bool child2_is_directory)
+{
+	unsigned long access_bit;
+
+	for (access_bit = 0; access_bit < ARRAY_SIZE(*layer_masks_parent2);
+	     access_bit++) {
+		/* Ignores accesses that only make sense for directories. */
+		const bool is_file_access =
+			!!(BIT_ULL(access_bit) & ACCESS_FILE);
+
+		if (child1_is_directory || is_file_access) {
+			/*
+			 * Checks if the destination restrictions are a
+			 * superset of the source ones (i.e. inherited access
+			 * rights without child exceptions):
+			 * restrictions(parent2) >= restrictions(child1)
+			 */
+			if ((((*layer_masks_parent1)[access_bit] &
+			      (*layer_masks_child1)[access_bit]) |
+			     (*layer_masks_parent2)[access_bit]) !=
+			    (*layer_masks_parent2)[access_bit])
+				return false;
+		}
+
+		if (!layer_masks_child2)
+			continue;
+		if (child2_is_directory || is_file_access) {
+			/*
+			 * Checks inverted restrictions for RENAME_EXCHANGE:
+			 * restrictions(parent1) >= restrictions(child2)
+			 */
+			if ((((*layer_masks_parent2)[access_bit] &
+			      (*layer_masks_child2)[access_bit]) |
+			     (*layer_masks_parent1)[access_bit]) !=
+			    (*layer_masks_parent1)[access_bit])
+				return false;
+		}
+	}
+	return true;
+}
+
+/*
+ * Removes @layer_masks accesses that are not requested.
+ *
+ * Returns true if the request is allowed, false otherwise.
+ */
+static inline bool
+scope_to_request(const access_mask_t access_request,
+		 layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
+{
+	const unsigned long access_req = access_request;
+	unsigned long access_bit;
+
+	if (WARN_ON_ONCE(!layer_masks))
+		return true;
+
+	for_each_clear_bit(access_bit, &access_req, ARRAY_SIZE(*layer_masks))
+		(*layer_masks)[access_bit] = 0;
+	return !memchr_inv(layer_masks, 0, sizeof(*layer_masks));
+}
+
+/*
+ * Returns true if there is at least one access right different than
+ * LANDLOCK_ACCESS_FS_REFER.
+ */
+static inline bool
+is_eacces(const layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS],
+	  const access_mask_t access_request)
+{
+	unsigned long access_bit;
+	/* LANDLOCK_ACCESS_FS_REFER alone must return -EXDEV. */
+	const unsigned long access_check = access_request &
+					   ~LANDLOCK_ACCESS_FS_REFER;
+
+	if (!layer_masks)
+		return false;
+
+	for_each_set_bit(access_bit, &access_check, ARRAY_SIZE(*layer_masks)) {
+		if ((*layer_masks)[access_bit])
+			return true;
+	}
+	return false;
+}
+
+/**
+ * check_access_path_dual - Check accesses for requests with a common path
+ *
+ * @domain: Domain to check against.
+ * @path: File hierarchy to walk through.
+ * @access_request_parent1: Accesses to check, once @layer_masks_parent1 is
+ *     equal to @layer_masks_parent2 (if any).  This is tied to the unique
+ *     requested path for most actions, or the source in case of a refer action
+ *     (i.e. rename or link), or the source and destination in case of
+ *     RENAME_EXCHANGE.
+ * @layer_masks_parent1: Pointer to a matrix of layer masks per access
+ *     masks, identifying the layers that forbid a specific access.  Bits from
+ *     this matrix can be unset according to the @path walk.  An empty matrix
+ *     means that @domain allows all possible Landlock accesses (i.e. not only
+ *     those identified by @access_request_parent1).  This matrix can
+ *     initially refer to domain layer masks and, when the accesses for the
+ *     destination and source are the same, to requested layer masks.
+ * @dentry_child1: Dentry to the initial child of the parent1 path.  This
+ *     pointer must be NULL for non-refer actions (i.e. not link nor rename).
+ * @access_request_parent2: Similar to @access_request_parent1 but for a
+ *     request involving a source and a destination.  This refers to the
+ *     destination, except in case of RENAME_EXCHANGE where it also refers to
+ *     the source.  Must be set to 0 when using a simple path request.
+ * @layer_masks_parent2: Similar to @layer_masks_parent1 but for a refer
+ *     action.  This must be NULL otherwise.
+ * @dentry_child2: Dentry to the initial child of the parent2 path.  This
+ *     pointer is only set for RENAME_EXCHANGE actions and must be NULL
+ *     otherwise.
+ *
+ * This helper first checks that the destination has a superset of restrictions
+ * compared to the source (if any) for a common path.  Because of
+ * RENAME_EXCHANGE actions, source and destinations may be swapped.  It then
+ * checks that the collected accesses and the remaining ones are enough to
+ * allow the request.
+ *
+ * Returns:
+ * - 0 if the access request is granted;
+ * - -EACCES if it is denied because of access right other than
+ *   LANDLOCK_ACCESS_FS_REFER;
+ * - -EXDEV if the renaming or linking would be a privileged escalation
+ *   (according to each layered policies), or if LANDLOCK_ACCESS_FS_REFER is
+ *   not allowed by the source or the destination.
+ */
+static int check_access_path_dual(
+	const struct landlock_ruleset *const domain,
+	const struct path *const path,
+	const access_mask_t access_request_parent1,
+	layer_mask_t (*const layer_masks_parent1)[LANDLOCK_NUM_ACCESS_FS],
+	const struct dentry *const dentry_child1,
+	const access_mask_t access_request_parent2,
+	layer_mask_t (*const layer_masks_parent2)[LANDLOCK_NUM_ACCESS_FS],
+	const struct dentry *const dentry_child2)
+{
+	bool allowed_parent1 = false, allowed_parent2 = false, is_dom_check,
+	     child1_is_directory = true, child2_is_directory = true;
+	struct path walker_path;
+	access_mask_t access_masked_parent1, access_masked_parent2;
+	layer_mask_t _layer_masks_child1[LANDLOCK_NUM_ACCESS_FS],
+		_layer_masks_child2[LANDLOCK_NUM_ACCESS_FS];
+	layer_mask_t(*layer_masks_child1)[LANDLOCK_NUM_ACCESS_FS] = NULL,
+	(*layer_masks_child2)[LANDLOCK_NUM_ACCESS_FS] = NULL;
+
+	if (!access_request_parent1 && !access_request_parent2)
+		return 0;
 	if (WARN_ON_ONCE(!domain || !path))
 		return 0;
-	/*
-	 * Allows access to pseudo filesystems that will never be mountable
-	 * (e.g. sockfs, pipefs), but can still be reachable through
-	 * /proc/<pid>/fd/<file-descriptor> .
-	 */
-	if ((path->dentry->d_sb->s_flags & SB_NOUSER) ||
-			(d_is_positive(path->dentry) &&
-			 unlikely(IS_PRIVATE(d_backing_inode(path->dentry)))))
+	if (is_nouser_or_private(path->dentry))
 		return 0;
-	if (WARN_ON_ONCE(domain->num_layers < 1))
+	if (WARN_ON_ONCE(domain->num_layers < 1 || !layer_masks_parent1))
 		return -EACCES;
 
-	/* Saves all layers handling a subset of requested accesses. */
-	layer_mask = 0;
-	for (i = 0; i < domain->num_layers; i++) {
-		if (domain->fs_access_masks[i] & access_request)
-			layer_mask |= BIT_ULL(i);
+	if (unlikely(layer_masks_parent2)) {
+		if (WARN_ON_ONCE(!dentry_child1))
+			return -EACCES;
+		/*
+		 * For a double request, first check for potential privilege
+		 * escalation by looking at domain handled accesses (which are
+		 * a superset of the meaningful requested accesses).
+		 */
+		access_masked_parent1 = access_masked_parent2 =
+			get_handled_accesses(domain);
+		is_dom_check = true;
+	} else {
+		if (WARN_ON_ONCE(dentry_child1 || dentry_child2))
+			return -EACCES;
+		/* For a simple request, only check for requested accesses. */
+		access_masked_parent1 = access_request_parent1;
+		access_masked_parent2 = access_request_parent2;
+		is_dom_check = false;
+	}
+
+	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 = &_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 = &_layer_masks_child2;
+		child2_is_directory = d_is_dir(dentry_child2);
 	}
-	/* An access request not handled by the domain is allowed. */
-	if (layer_mask == 0)
-		return 0;
 
 	walker_path = *path;
 	path_get(&walker_path);
@@ -267,15 +539,54 @@ static int check_access_path(const struct landlock_ruleset *const domain,
 	 */
 	while (true) {
 		struct dentry *parent_dentry;
+		const struct landlock_rule *rule;
 
-		layer_mask = unmask_layers(domain, &walker_path,
-				access_request, layer_mask);
-		if (layer_mask == 0) {
-			/* Stops when a rule from each layer grants access. */
-			allowed = true;
-			break;
+		/*
+		 * If at least all accesses allowed on the destination are
+		 * already allowed on the source, respectively if there is at
+		 * least as much as restrictions on the destination than on the
+		 * source, then we can safely refer files from the source to
+		 * the destination without risking a privilege escalation.
+		 * This also applies in the case of RENAME_EXCHANGE, which
+		 * implies checks on both direction.  This is crucial for
+		 * standalone multilayered security policies.  Furthermore,
+		 * this helps avoid policy writers to shoot themselves in the
+		 * foot.
+		 */
+		if (unlikely(is_dom_check &&
+			     no_more_access(
+				     layer_masks_parent1, layer_masks_child1,
+				     child1_is_directory, layer_masks_parent2,
+				     layer_masks_child2,
+				     child2_is_directory))) {
+			allowed_parent1 = scope_to_request(
+				access_request_parent1, layer_masks_parent1);
+			allowed_parent2 = scope_to_request(
+				access_request_parent2, layer_masks_parent2);
+
+			/* Stops when all accesses are granted. */
+			if (allowed_parent1 && allowed_parent2)
+				break;
+
+			/*
+			 * Now, downgrades the remaining checks from domain
+			 * handled accesses to requested accesses.
+			 */
+			is_dom_check = false;
+			access_masked_parent1 = access_request_parent1;
+			access_masked_parent2 = access_request_parent2;
 		}
 
+		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);
+
+		/* 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)) {
@@ -286,7 +597,6 @@ jump_up:
 				 * Stops at the real root.  Denies access
 				 * because not all layers have granted access.
 				 */
-				allowed = false;
 				break;
 			}
 		}
@@ -296,7 +606,8 @@ jump_up:
 			 * access to internal filesystems (e.g. nsfs, which is
 			 * reachable through /proc/<pid>/ns/<namespace>).
 			 */
-			allowed = !!(walker_path.mnt->mnt_flags & MNT_INTERNAL);
+			allowed_parent1 = allowed_parent2 =
+				!!(walker_path.mnt->mnt_flags & MNT_INTERNAL);
 			break;
 		}
 		parent_dentry = dget_parent(walker_path.dentry);
@@ -304,11 +615,40 @@ jump_up:
 		walker_path.dentry = parent_dentry;
 	}
 	path_put(&walker_path);
-	return allowed ? 0 : -EACCES;
+
+	if (allowed_parent1 && allowed_parent2)
+		return 0;
+
+	/*
+	 * This prioritizes EACCES over EXDEV for all actions, including
+	 * renames with RENAME_EXCHANGE.
+	 */
+	if (likely(is_eacces(layer_masks_parent1, access_request_parent1) ||
+		   is_eacces(layer_masks_parent2, access_request_parent2)))
+		return -EACCES;
+
+	/*
+	 * Gracefully forbids reparenting if the destination directory
+	 * hierarchy is not a superset of restrictions of the source directory
+	 * hierarchy, or if LANDLOCK_ACCESS_FS_REFER is not allowed by the
+	 * source or the destination.
+	 */
+	return -EXDEV;
+}
+
+static inline int check_access_path(const struct landlock_ruleset *const domain,
+				    const struct path *const path,
+				    access_mask_t access_request)
+{
+	layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {};
+
+	access_request = init_layer_masks(domain, access_request, &layer_masks);
+	return check_access_path_dual(domain, path, access_request,
+				      &layer_masks, NULL, 0, NULL, NULL);
 }
 
 static inline int current_check_access_path(const struct path *const path,
-		const u32 access_request)
+					    const access_mask_t access_request)
 {
 	const struct landlock_ruleset *const dom =
 		landlock_get_current_domain();
@@ -318,6 +658,239 @@ static inline int current_check_access_path(const struct path *const path,
 	return check_access_path(dom, path, access_request);
 }
 
+static inline access_mask_t get_mode_access(const umode_t mode)
+{
+	switch (mode & S_IFMT) {
+	case S_IFLNK:
+		return LANDLOCK_ACCESS_FS_MAKE_SYM;
+	case 0:
+		/* A zero mode translates to S_IFREG. */
+	case S_IFREG:
+		return LANDLOCK_ACCESS_FS_MAKE_REG;
+	case S_IFDIR:
+		return LANDLOCK_ACCESS_FS_MAKE_DIR;
+	case S_IFCHR:
+		return LANDLOCK_ACCESS_FS_MAKE_CHAR;
+	case S_IFBLK:
+		return LANDLOCK_ACCESS_FS_MAKE_BLOCK;
+	case S_IFIFO:
+		return LANDLOCK_ACCESS_FS_MAKE_FIFO;
+	case S_IFSOCK:
+		return LANDLOCK_ACCESS_FS_MAKE_SOCK;
+	default:
+		WARN_ON_ONCE(1);
+		return 0;
+	}
+}
+
+static inline access_mask_t maybe_remove(const struct dentry *const dentry)
+{
+	if (d_is_negative(dentry))
+		return 0;
+	return d_is_dir(dentry) ? LANDLOCK_ACCESS_FS_REMOVE_DIR :
+				  LANDLOCK_ACCESS_FS_REMOVE_FILE;
+}
+
+/**
+ * collect_domain_accesses - Walk through a file path and collect accesses
+ *
+ * @domain: Domain to check against.
+ * @mnt_root: Last directory to check.
+ * @dir: Directory to start the walk from.
+ * @layer_masks_dom: Where to store the collected accesses.
+ *
+ * This helper is useful to begin a path walk from the @dir directory to a
+ * @mnt_root directory used as a mount point.  This mount point is the common
+ * ancestor between the source and the destination of a renamed and linked
+ * file.  While walking from @dir to @mnt_root, we record all the domain's
+ * allowed accesses in @layer_masks_dom.
+ *
+ * This is similar to check_access_path_dual() but much simpler because it only
+ * handles walking on the same mount point and only check one set of accesses.
+ *
+ * Returns:
+ * - true if all the domain access rights are allowed for @dir;
+ * - false if the walk reached @mnt_root.
+ */
+static bool collect_domain_accesses(
+	const struct landlock_ruleset *const domain,
+	const struct dentry *const mnt_root, struct dentry *dir,
+	layer_mask_t (*const layer_masks_dom)[LANDLOCK_NUM_ACCESS_FS])
+{
+	unsigned long access_dom;
+	bool ret = false;
+
+	if (WARN_ON_ONCE(!domain || !mnt_root || !dir || !layer_masks_dom))
+		return true;
+	if (is_nouser_or_private(dir))
+		return true;
+
+	access_dom = init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
+				      layer_masks_dom);
+
+	dget(dir);
+	while (true) {
+		struct dentry *parent_dentry;
+
+		/* Gets all layers allowing all domain accesses. */
+		if (unmask_layers(find_rule(domain, dir), access_dom,
+				  layer_masks_dom)) {
+			/*
+			 * Stops when all handled accesses are allowed by at
+			 * least one rule in each layer.
+			 */
+			ret = true;
+			break;
+		}
+
+		/* We should not reach a root other than @mnt_root. */
+		if (dir == mnt_root || WARN_ON_ONCE(IS_ROOT(dir)))
+			break;
+
+		parent_dentry = dget_parent(dir);
+		dput(dir);
+		dir = parent_dentry;
+	}
+	dput(dir);
+	return ret;
+}
+
+/**
+ * current_check_refer_path - Check if a rename or link action is allowed
+ *
+ * @old_dentry: File or directory requested to be moved or linked.
+ * @new_dir: Destination parent directory.
+ * @new_dentry: Destination file or directory.
+ * @removable: Sets to true if it is a rename operation.
+ * @exchange: Sets to true if it is a rename operation with RENAME_EXCHANGE.
+ *
+ * Because of its unprivileged constraints, Landlock relies on file hierarchies
+ * (and not only inodes) to tie access rights to files.  Being able to link or
+ * rename a file hierarchy brings some challenges.  Indeed, moving or linking a
+ * file (i.e. creating a new reference to an inode) can have an impact on the
+ * actions allowed for a set of files if it would change its parent directory
+ * (i.e. reparenting).
+ *
+ * To avoid trivial access right bypasses, Landlock first checks if the file or
+ * directory requested to be moved would gain new access rights inherited from
+ * its new hierarchy.  Before returning any error, Landlock then checks that
+ * the parent source hierarchy and the destination hierarchy would allow the
+ * link or rename action.  If it is not the case, an error with EACCES is
+ * returned to inform user space that there is no way to remove or create the
+ * requested source file type.  If it should be allowed but the new inherited
+ * access rights would be greater than the source access rights, then the
+ * kernel returns an error with EXDEV.  Prioritizing EACCES over EXDEV enables
+ * user space to abort the whole operation if there is no way to do it, or to
+ * manually copy the source to the destination if this remains allowed, e.g.
+ * because file creation is allowed on the destination directory but not direct
+ * linking.
+ *
+ * To achieve this goal, the kernel needs to compare two file hierarchies: the
+ * one identifying the source file or directory (including itself), and the
+ * destination one.  This can be seen as a multilayer partial ordering problem.
+ * The kernel walks through these paths and collects in a matrix the access
+ * rights that are denied per layer.  These matrices are then compared to see
+ * if the destination one has more (or the same) restrictions as the source
+ * one.  If this is the case, the requested action will not return EXDEV, which
+ * doesn't mean the action is allowed.  The parent hierarchy of the source
+ * (i.e. parent directory), and the destination hierarchy must also be checked
+ * to verify that they explicitly allow such action (i.e.  referencing,
+ * creation and potentially removal rights).  The kernel implementation is then
+ * required to rely on potentially four matrices of access rights: one for the
+ * source file or directory (i.e. the child), a potentially other one for the
+ * other source/destination (in case of RENAME_EXCHANGE), one for the source
+ * parent hierarchy and a last one for the destination hierarchy.  These
+ * ephemeral matrices take some space on the stack, which limits the number of
+ * layers to a deemed reasonable number: 16.
+ *
+ * Returns:
+ * - 0 if access is allowed;
+ * - -EXDEV if @old_dentry would inherit new access rights from @new_dir;
+ * - -EACCES if file removal or creation is denied.
+ */
+static int current_check_refer_path(struct dentry *const old_dentry,
+				    const struct path *const new_dir,
+				    struct dentry *const new_dentry,
+				    const bool removable, const bool exchange)
+{
+	const struct landlock_ruleset *const dom =
+		landlock_get_current_domain();
+	bool allow_parent1, allow_parent2;
+	access_mask_t access_request_parent1, access_request_parent2;
+	struct path mnt_dir;
+	layer_mask_t layer_masks_parent1[LANDLOCK_NUM_ACCESS_FS],
+		layer_masks_parent2[LANDLOCK_NUM_ACCESS_FS];
+
+	if (!dom)
+		return 0;
+	if (WARN_ON_ONCE(dom->num_layers < 1))
+		return -EACCES;
+	if (unlikely(d_is_negative(old_dentry)))
+		return -ENOENT;
+	if (exchange) {
+		if (unlikely(d_is_negative(new_dentry)))
+			return -ENOENT;
+		access_request_parent1 =
+			get_mode_access(d_backing_inode(new_dentry)->i_mode);
+	} else {
+		access_request_parent1 = 0;
+	}
+	access_request_parent2 =
+		get_mode_access(d_backing_inode(old_dentry)->i_mode);
+	if (removable) {
+		access_request_parent1 |= maybe_remove(old_dentry);
+		access_request_parent2 |= maybe_remove(new_dentry);
+	}
+
+	/* The mount points are the same for old and new paths, cf. EXDEV. */
+	if (old_dentry->d_parent == new_dir->dentry) {
+		/*
+		 * The LANDLOCK_ACCESS_FS_REFER access right is not required
+		 * for same-directory referer (i.e. no reparenting).
+		 */
+		access_request_parent1 = init_layer_masks(
+			dom, access_request_parent1 | access_request_parent2,
+			&layer_masks_parent1);
+		return check_access_path_dual(dom, new_dir,
+					      access_request_parent1,
+					      &layer_masks_parent1, NULL, 0,
+					      NULL, NULL);
+	}
+
+	/* Backward compatibility: no reparenting support. */
+	if (!(get_handled_accesses(dom) & LANDLOCK_ACCESS_FS_REFER))
+		return -EXDEV;
+
+	access_request_parent1 |= LANDLOCK_ACCESS_FS_REFER;
+	access_request_parent2 |= LANDLOCK_ACCESS_FS_REFER;
+
+	/* Saves the common mount point. */
+	mnt_dir.mnt = new_dir->mnt;
+	mnt_dir.dentry = new_dir->mnt->mnt_root;
+
+	/* new_dir->dentry is equal to new_dentry->d_parent */
+	allow_parent1 = collect_domain_accesses(dom, mnt_dir.dentry,
+						old_dentry->d_parent,
+						&layer_masks_parent1);
+	allow_parent2 = collect_domain_accesses(
+		dom, mnt_dir.dentry, new_dir->dentry, &layer_masks_parent2);
+
+	if (allow_parent1 && allow_parent2)
+		return 0;
+
+	/*
+	 * To be able to compare source and destination domain access rights,
+	 * take into account the @old_dentry access rights aggregated with its
+	 * parent access rights.  This will be useful to compare with the
+	 * destination parent access rights.
+	 */
+	return check_access_path_dual(dom, &mnt_dir, access_request_parent1,
+				      &layer_masks_parent1, old_dentry,
+				      access_request_parent2,
+				      &layer_masks_parent2,
+				      exchange ? new_dentry : NULL);
+}
+
 /* Inode hooks */
 
 static void hook_inode_free_security(struct inode *const inode)
@@ -436,8 +1009,8 @@ static void hook_sb_delete(struct super_block *const sb)
 	if (prev_inode)
 		iput(prev_inode);
 	/* Waits for pending iput() in release_inode(). */
-	wait_var_event(&landlock_superblock(sb)->inode_refs, !atomic_long_read(
-				&landlock_superblock(sb)->inode_refs));
+	wait_var_event(&landlock_superblock(sb)->inode_refs,
+		       !atomic_long_read(&landlock_superblock(sb)->inode_refs));
 }
 
 /*
@@ -459,8 +1032,8 @@ static void hook_sb_delete(struct super_block *const sb)
  * a dedicated user space option would be required (e.g. as a ruleset flag).
  */
 static int hook_sb_mount(const char *const dev_name,
-		const struct path *const path, const char *const type,
-		const unsigned long flags, void *const data)
+			 const struct path *const path, const char *const type,
+			 const unsigned long flags, void *const data)
 {
 	if (!landlock_get_current_domain())
 		return 0;
@@ -468,7 +1041,7 @@ static int hook_sb_mount(const char *const dev_name,
 }
 
 static int hook_move_mount(const struct path *const from_path,
-		const struct path *const to_path)
+			   const struct path *const to_path)
 {
 	if (!landlock_get_current_domain())
 		return 0;
@@ -502,7 +1075,7 @@ static int hook_sb_remount(struct super_block *const sb, void *const mnt_opts)
  * view of the filesystem.
  */
 static int hook_sb_pivotroot(const struct path *const old_path,
-		const struct path *const new_path)
+			     const struct path *const new_path)
 {
 	if (!landlock_get_current_domain())
 		return 0;
@@ -511,97 +1084,34 @@ static int hook_sb_pivotroot(const struct path *const old_path,
 
 /* Path hooks */
 
-static inline u32 get_mode_access(const umode_t mode)
-{
-	switch (mode & S_IFMT) {
-	case S_IFLNK:
-		return LANDLOCK_ACCESS_FS_MAKE_SYM;
-	case 0:
-		/* A zero mode translates to S_IFREG. */
-	case S_IFREG:
-		return LANDLOCK_ACCESS_FS_MAKE_REG;
-	case S_IFDIR:
-		return LANDLOCK_ACCESS_FS_MAKE_DIR;
-	case S_IFCHR:
-		return LANDLOCK_ACCESS_FS_MAKE_CHAR;
-	case S_IFBLK:
-		return LANDLOCK_ACCESS_FS_MAKE_BLOCK;
-	case S_IFIFO:
-		return LANDLOCK_ACCESS_FS_MAKE_FIFO;
-	case S_IFSOCK:
-		return LANDLOCK_ACCESS_FS_MAKE_SOCK;
-	default:
-		WARN_ON_ONCE(1);
-		return 0;
-	}
-}
-
-/*
- * Creating multiple links or renaming may lead to privilege escalations if not
- * handled properly.  Indeed, we must be sure that the source doesn't gain more
- * privileges by being accessible from the destination.  This is getting more
- * complex when dealing with multiple layers.  The whole picture can be seen as
- * a multilayer partial ordering problem.  A future version of Landlock will
- * deal with that.
- */
 static int hook_path_link(struct dentry *const old_dentry,
-		const struct path *const new_dir,
-		struct dentry *const new_dentry)
-{
-	const struct landlock_ruleset *const dom =
-		landlock_get_current_domain();
-
-	if (!dom)
-		return 0;
-	/* The mount points are the same for old and new paths, cf. EXDEV. */
-	if (old_dentry->d_parent != new_dir->dentry)
-		/* Gracefully forbids reparenting. */
-		return -EXDEV;
-	if (unlikely(d_is_negative(old_dentry)))
-		return -ENOENT;
-	return check_access_path(dom, new_dir,
-			get_mode_access(d_backing_inode(old_dentry)->i_mode));
-}
-
-static inline u32 maybe_remove(const struct dentry *const dentry)
+			  const struct path *const new_dir,
+			  struct dentry *const new_dentry)
 {
-	if (d_is_negative(dentry))
-		return 0;
-	return d_is_dir(dentry) ? LANDLOCK_ACCESS_FS_REMOVE_DIR :
-		LANDLOCK_ACCESS_FS_REMOVE_FILE;
+	return current_check_refer_path(old_dentry, new_dir, new_dentry, false,
+					false);
 }
 
 static int hook_path_rename(const struct path *const old_dir,
-		struct dentry *const old_dentry,
-		const struct path *const new_dir,
-		struct dentry *const new_dentry)
+			    struct dentry *const old_dentry,
+			    const struct path *const new_dir,
+			    struct dentry *const new_dentry,
+			    const unsigned int flags)
 {
-	const struct landlock_ruleset *const dom =
-		landlock_get_current_domain();
-
-	if (!dom)
-		return 0;
-	/* The mount points are the same for old and new paths, cf. EXDEV. */
-	if (old_dir->dentry != new_dir->dentry)
-		/* Gracefully forbids reparenting. */
-		return -EXDEV;
-	if (unlikely(d_is_negative(old_dentry)))
-		return -ENOENT;
-	/* RENAME_EXCHANGE is handled because directories are the same. */
-	return check_access_path(dom, old_dir, maybe_remove(old_dentry) |
-			maybe_remove(new_dentry) |
-			get_mode_access(d_backing_inode(old_dentry)->i_mode));
+	/* old_dir refers to old_dentry->d_parent and new_dir->mnt */
+	return current_check_refer_path(old_dentry, new_dir, new_dentry, true,
+					!!(flags & RENAME_EXCHANGE));
 }
 
 static int hook_path_mkdir(const struct path *const dir,
-		struct dentry *const dentry, const umode_t mode)
+			   struct dentry *const dentry, const umode_t mode)
 {
 	return current_check_access_path(dir, LANDLOCK_ACCESS_FS_MAKE_DIR);
 }
 
 static int hook_path_mknod(const struct path *const dir,
-		struct dentry *const dentry, const umode_t mode,
-		const unsigned int dev)
+			   struct dentry *const dentry, const umode_t mode,
+			   const unsigned int dev)
 {
 	const struct landlock_ruleset *const dom =
 		landlock_get_current_domain();
@@ -612,28 +1122,29 @@ static int hook_path_mknod(const struct path *const dir,
 }
 
 static int hook_path_symlink(const struct path *const dir,
-		struct dentry *const dentry, const char *const old_name)
+			     struct dentry *const dentry,
+			     const char *const old_name)
 {
 	return current_check_access_path(dir, LANDLOCK_ACCESS_FS_MAKE_SYM);
 }
 
 static int hook_path_unlink(const struct path *const dir,
-		struct dentry *const dentry)
+			    struct dentry *const dentry)
 {
 	return current_check_access_path(dir, LANDLOCK_ACCESS_FS_REMOVE_FILE);
 }
 
 static int hook_path_rmdir(const struct path *const dir,
-		struct dentry *const dentry)
+			   struct dentry *const dentry)
 {
 	return current_check_access_path(dir, LANDLOCK_ACCESS_FS_REMOVE_DIR);
 }
 
 /* File hooks */
 
-static inline u32 get_file_access(const struct file *const file)
+static inline access_mask_t get_file_access(const struct file *const file)
 {
-	u32 access = 0;
+	access_mask_t access = 0;
 
 	if (file->f_mode & FMODE_READ) {
 		/* A directory can only be opened in read mode. */
@@ -688,5 +1199,5 @@ static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = {
 __init void landlock_add_fs_hooks(void)
 {
 	security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
-			LANDLOCK_NAME);
+			   LANDLOCK_NAME);
 }
diff --git a/security/landlock/fs.h b/security/landlock/fs.h
index 187284b421c9..8db7acf9109b 100644
--- a/security/landlock/fs.h
+++ b/security/landlock/fs.h
@@ -50,14 +50,14 @@ struct landlock_superblock_security {
 	atomic_long_t inode_refs;
 };
 
-static inline struct landlock_inode_security *landlock_inode(
-		const struct inode *const inode)
+static inline struct landlock_inode_security *
+landlock_inode(const struct inode *const inode)
 {
 	return inode->i_security + landlock_blob_sizes.lbs_inode;
 }
 
-static inline struct landlock_superblock_security *landlock_superblock(
-		const struct super_block *const superblock)
+static inline struct landlock_superblock_security *
+landlock_superblock(const struct super_block *const superblock)
 {
 	return superblock->s_security + landlock_blob_sizes.lbs_superblock;
 }
@@ -65,6 +65,7 @@ static inline struct landlock_superblock_security *landlock_superblock(
 __init void landlock_add_fs_hooks(void);
 
 int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
-		const struct path *const path, u32 access_hierarchy);
+			    const struct path *const path,
+			    access_mask_t access_hierarchy);
 
 #endif /* _SECURITY_LANDLOCK_FS_H */
diff --git a/security/landlock/limits.h b/security/landlock/limits.h
index 2a0a1095ee27..b54184ab9439 100644
--- a/security/landlock/limits.h
+++ b/security/landlock/limits.h
@@ -9,13 +9,19 @@
 #ifndef _SECURITY_LANDLOCK_LIMITS_H
 #define _SECURITY_LANDLOCK_LIMITS_H
 
+#include <linux/bitops.h>
 #include <linux/limits.h>
 #include <uapi/linux/landlock.h>
 
-#define LANDLOCK_MAX_NUM_LAYERS		64
+/* clang-format off */
+
+#define LANDLOCK_MAX_NUM_LAYERS		16
 #define LANDLOCK_MAX_NUM_RULES		U32_MAX
 
-#define LANDLOCK_LAST_ACCESS_FS		LANDLOCK_ACCESS_FS_MAKE_SYM
+#define LANDLOCK_LAST_ACCESS_FS		LANDLOCK_ACCESS_FS_REFER
 #define LANDLOCK_MASK_ACCESS_FS		((LANDLOCK_LAST_ACCESS_FS << 1) - 1)
+#define LANDLOCK_NUM_ACCESS_FS		__const_hweight64(LANDLOCK_MASK_ACCESS_FS)
+
+/* clang-format on */
 
 #endif /* _SECURITY_LANDLOCK_LIMITS_H */
diff --git a/security/landlock/object.c b/security/landlock/object.c
index d674fdf9ff04..1f50612f0185 100644
--- a/security/landlock/object.c
+++ b/security/landlock/object.c
@@ -17,9 +17,9 @@
 
 #include "object.h"
 
-struct landlock_object *landlock_create_object(
-		const struct landlock_object_underops *const underops,
-		void *const underobj)
+struct landlock_object *
+landlock_create_object(const struct landlock_object_underops *const underops,
+		       void *const underobj)
 {
 	struct landlock_object *new_object;
 
diff --git a/security/landlock/object.h b/security/landlock/object.h
index 3f80674c6c8d..5f28c35e8aa8 100644
--- a/security/landlock/object.h
+++ b/security/landlock/object.h
@@ -76,9 +76,9 @@ struct landlock_object {
 	};
 };
 
-struct landlock_object *landlock_create_object(
-		const struct landlock_object_underops *const underops,
-		void *const underobj);
+struct landlock_object *
+landlock_create_object(const struct landlock_object_underops *const underops,
+		       void *const underobj);
 
 void landlock_put_object(struct landlock_object *const object);
 
diff --git a/security/landlock/ptrace.c b/security/landlock/ptrace.c
index f55b82446de2..4c5b9cd71286 100644
--- a/security/landlock/ptrace.c
+++ b/security/landlock/ptrace.c
@@ -30,7 +30,7 @@
  * means a subset of) the @child domain.
  */
 static bool domain_scope_le(const struct landlock_ruleset *const parent,
-		const struct landlock_ruleset *const child)
+			    const struct landlock_ruleset *const child)
 {
 	const struct landlock_hierarchy *walker;
 
@@ -48,7 +48,7 @@ static bool domain_scope_le(const struct landlock_ruleset *const parent,
 }
 
 static bool task_is_scoped(const struct task_struct *const parent,
-		const struct task_struct *const child)
+			   const struct task_struct *const child)
 {
 	bool is_scoped;
 	const struct landlock_ruleset *dom_parent, *dom_child;
@@ -62,7 +62,7 @@ static bool task_is_scoped(const struct task_struct *const parent,
 }
 
 static int task_ptrace(const struct task_struct *const parent,
-		const struct task_struct *const child)
+		       const struct task_struct *const child)
 {
 	/* Quick return for non-landlocked tasks. */
 	if (!landlocked(parent))
@@ -86,7 +86,7 @@ static int task_ptrace(const struct task_struct *const parent,
  * granted, -errno if denied.
  */
 static int hook_ptrace_access_check(struct task_struct *const child,
-		const unsigned int mode)
+				    const unsigned int mode)
 {
 	return task_ptrace(current, child);
 }
@@ -116,5 +116,5 @@ static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = {
 __init void landlock_add_ptrace_hooks(void)
 {
 	security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
-			LANDLOCK_NAME);
+			   LANDLOCK_NAME);
 }
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index ec72b9262bf3..996484f98bfd 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -28,8 +28,9 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
 {
 	struct landlock_ruleset *new_ruleset;
 
-	new_ruleset = kzalloc(struct_size(new_ruleset, fs_access_masks,
-				num_layers), GFP_KERNEL_ACCOUNT);
+	new_ruleset =
+		kzalloc(struct_size(new_ruleset, fs_access_masks, num_layers),
+			GFP_KERNEL_ACCOUNT);
 	if (!new_ruleset)
 		return ERR_PTR(-ENOMEM);
 	refcount_set(&new_ruleset->usage, 1);
@@ -44,7 +45,8 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
 	return new_ruleset;
 }
 
-struct landlock_ruleset *landlock_create_ruleset(const u32 fs_access_mask)
+struct landlock_ruleset *
+landlock_create_ruleset(const access_mask_t fs_access_mask)
 {
 	struct landlock_ruleset *new_ruleset;
 
@@ -66,11 +68,10 @@ static void build_check_rule(void)
 	BUILD_BUG_ON(rule.num_layers < LANDLOCK_MAX_NUM_LAYERS);
 }
 
-static struct landlock_rule *create_rule(
-		struct landlock_object *const object,
-		const struct landlock_layer (*const layers)[],
-		const u32 num_layers,
-		const struct landlock_layer *const new_layer)
+static struct landlock_rule *
+create_rule(struct landlock_object *const object,
+	    const struct landlock_layer (*const layers)[], const u32 num_layers,
+	    const struct landlock_layer *const new_layer)
 {
 	struct landlock_rule *new_rule;
 	u32 new_num_layers;
@@ -85,7 +86,7 @@ static struct landlock_rule *create_rule(
 		new_num_layers = num_layers;
 	}
 	new_rule = kzalloc(struct_size(new_rule, layers, new_num_layers),
-			GFP_KERNEL_ACCOUNT);
+			   GFP_KERNEL_ACCOUNT);
 	if (!new_rule)
 		return ERR_PTR(-ENOMEM);
 	RB_CLEAR_NODE(&new_rule->node);
@@ -94,7 +95,7 @@ static struct landlock_rule *create_rule(
 	new_rule->num_layers = new_num_layers;
 	/* Copies the original layer stack. */
 	memcpy(new_rule->layers, layers,
-			flex_array_size(new_rule, layers, num_layers));
+	       flex_array_size(new_rule, layers, num_layers));
 	if (new_layer)
 		/* Adds a copy of @new_layer on the layer stack. */
 		new_rule->layers[new_rule->num_layers - 1] = *new_layer;
@@ -142,9 +143,9 @@ static void build_check_ruleset(void)
  * access rights.
  */
 static int insert_rule(struct landlock_ruleset *const ruleset,
-		struct landlock_object *const object,
-		const struct landlock_layer (*const layers)[],
-		size_t num_layers)
+		       struct landlock_object *const object,
+		       const struct landlock_layer (*const layers)[],
+		       size_t num_layers)
 {
 	struct rb_node **walker_node;
 	struct rb_node *parent_node = NULL;
@@ -156,8 +157,8 @@ static int insert_rule(struct landlock_ruleset *const ruleset,
 		return -ENOENT;
 	walker_node = &(ruleset->root.rb_node);
 	while (*walker_node) {
-		struct landlock_rule *const this = rb_entry(*walker_node,
-				struct landlock_rule, node);
+		struct landlock_rule *const this =
+			rb_entry(*walker_node, struct landlock_rule, node);
 
 		if (this->object != object) {
 			parent_node = *walker_node;
@@ -194,7 +195,7 @@ static int insert_rule(struct landlock_ruleset *const ruleset,
 		 * ruleset and a domain.
 		 */
 		new_rule = create_rule(object, &this->layers, this->num_layers,
-				&(*layers)[0]);
+				       &(*layers)[0]);
 		if (IS_ERR(new_rule))
 			return PTR_ERR(new_rule);
 		rb_replace_node(&this->node, &new_rule->node, &ruleset->root);
@@ -228,13 +229,14 @@ static void build_check_layer(void)
 
 /* @ruleset must be locked by the caller. */
 int landlock_insert_rule(struct landlock_ruleset *const ruleset,
-		struct landlock_object *const object, const u32 access)
+			 struct landlock_object *const object,
+			 const access_mask_t access)
 {
-	struct landlock_layer layers[] = {{
+	struct landlock_layer layers[] = { {
 		.access = access,
 		/* When @level is zero, insert_rule() extends @ruleset. */
 		.level = 0,
-	}};
+	} };
 
 	build_check_layer();
 	return insert_rule(ruleset, object, &layers, ARRAY_SIZE(layers));
@@ -257,7 +259,7 @@ static void put_hierarchy(struct landlock_hierarchy *hierarchy)
 }
 
 static int merge_ruleset(struct landlock_ruleset *const dst,
-		struct landlock_ruleset *const src)
+			 struct landlock_ruleset *const src)
 {
 	struct landlock_rule *walker_rule, *next_rule;
 	int err = 0;
@@ -282,11 +284,11 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
 	dst->fs_access_masks[dst->num_layers - 1] = src->fs_access_masks[0];
 
 	/* Merges the @src tree. */
-	rbtree_postorder_for_each_entry_safe(walker_rule, next_rule,
-			&src->root, node) {
-		struct landlock_layer layers[] = {{
+	rbtree_postorder_for_each_entry_safe(walker_rule, next_rule, &src->root,
+					     node) {
+		struct landlock_layer layers[] = { {
 			.level = dst->num_layers,
-		}};
+		} };
 
 		if (WARN_ON_ONCE(walker_rule->num_layers != 1)) {
 			err = -EINVAL;
@@ -298,7 +300,7 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
 		}
 		layers[0].access = walker_rule->layers[0].access;
 		err = insert_rule(dst, walker_rule->object, &layers,
-				ARRAY_SIZE(layers));
+				  ARRAY_SIZE(layers));
 		if (err)
 			goto out_unlock;
 	}
@@ -310,7 +312,7 @@ out_unlock:
 }
 
 static int inherit_ruleset(struct landlock_ruleset *const parent,
-		struct landlock_ruleset *const child)
+			   struct landlock_ruleset *const child)
 {
 	struct landlock_rule *walker_rule, *next_rule;
 	int err = 0;
@@ -325,9 +327,10 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
 
 	/* Copies the @parent tree. */
 	rbtree_postorder_for_each_entry_safe(walker_rule, next_rule,
-			&parent->root, node) {
+					     &parent->root, node) {
 		err = insert_rule(child, walker_rule->object,
-				&walker_rule->layers, walker_rule->num_layers);
+				  &walker_rule->layers,
+				  walker_rule->num_layers);
 		if (err)
 			goto out_unlock;
 	}
@@ -338,7 +341,7 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
 	}
 	/* Copies the parent layer stack and leaves a space for the new layer. */
 	memcpy(child->fs_access_masks, parent->fs_access_masks,
-			flex_array_size(parent, fs_access_masks, parent->num_layers));
+	       flex_array_size(parent, fs_access_masks, parent->num_layers));
 
 	if (WARN_ON_ONCE(!parent->hierarchy)) {
 		err = -EINVAL;
@@ -358,8 +361,7 @@ static void free_ruleset(struct landlock_ruleset *const ruleset)
 	struct landlock_rule *freeme, *next;
 
 	might_sleep();
-	rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root,
-			node)
+	rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root, node)
 		free_rule(freeme);
 	put_hierarchy(ruleset->hierarchy);
 	kfree(ruleset);
@@ -397,9 +399,9 @@ void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset)
  * Returns the intersection of @parent and @ruleset, or returns @parent if
  * @ruleset is empty, or returns a duplicate of @ruleset if @parent is empty.
  */
-struct landlock_ruleset *landlock_merge_ruleset(
-		struct landlock_ruleset *const parent,
-		struct landlock_ruleset *const ruleset)
+struct landlock_ruleset *
+landlock_merge_ruleset(struct landlock_ruleset *const parent,
+		       struct landlock_ruleset *const ruleset)
 {
 	struct landlock_ruleset *new_dom;
 	u32 num_layers;
@@ -421,8 +423,8 @@ struct landlock_ruleset *landlock_merge_ruleset(
 	new_dom = create_ruleset(num_layers);
 	if (IS_ERR(new_dom))
 		return new_dom;
-	new_dom->hierarchy = kzalloc(sizeof(*new_dom->hierarchy),
-			GFP_KERNEL_ACCOUNT);
+	new_dom->hierarchy =
+		kzalloc(sizeof(*new_dom->hierarchy), GFP_KERNEL_ACCOUNT);
 	if (!new_dom->hierarchy) {
 		err = -ENOMEM;
 		goto out_put_dom;
@@ -449,9 +451,9 @@ out_put_dom:
 /*
  * The returned access has the same lifetime as @ruleset.
  */
-const struct landlock_rule *landlock_find_rule(
-		const struct landlock_ruleset *const ruleset,
-		const struct landlock_object *const object)
+const struct landlock_rule *
+landlock_find_rule(const struct landlock_ruleset *const ruleset,
+		   const struct landlock_object *const object)
 {
 	const struct rb_node *node;
 
@@ -459,8 +461,8 @@ const struct landlock_rule *landlock_find_rule(
 		return NULL;
 	node = ruleset->root.rb_node;
 	while (node) {
-		struct landlock_rule *this = rb_entry(node,
-				struct landlock_rule, node);
+		struct landlock_rule *this =
+			rb_entry(node, struct landlock_rule, node);
 
 		if (this->object == object)
 			return this;
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index 2d3ed7ec5a0a..d43231b783e4 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -9,13 +9,26 @@
 #ifndef _SECURITY_LANDLOCK_RULESET_H
 #define _SECURITY_LANDLOCK_RULESET_H
 
+#include <linux/bitops.h>
+#include <linux/build_bug.h>
 #include <linux/mutex.h>
 #include <linux/rbtree.h>
 #include <linux/refcount.h>
 #include <linux/workqueue.h>
 
+#include "limits.h"
 #include "object.h"
 
+typedef u16 access_mask_t;
+/* Makes sure all filesystem access rights can be stored. */
+static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS);
+/* Makes sure for_each_set_bit() and for_each_clear_bit() calls are OK. */
+static_assert(sizeof(unsigned long) >= sizeof(access_mask_t));
+
+typedef u16 layer_mask_t;
+/* Makes sure all layers can be checked. */
+static_assert(BITS_PER_TYPE(layer_mask_t) >= LANDLOCK_MAX_NUM_LAYERS);
+
 /**
  * struct landlock_layer - Access rights for a given layer
  */
@@ -28,7 +41,7 @@ struct landlock_layer {
 	 * @access: Bitfield of allowed actions on the kernel object.  They are
 	 * relative to the object type (e.g. %LANDLOCK_ACTION_FS_READ).
 	 */
-	u16 access;
+	access_mask_t access;
 };
 
 /**
@@ -135,26 +148,28 @@ struct landlock_ruleset {
 			 * layers are set once and never changed for the
 			 * lifetime of the ruleset.
 			 */
-			u16 fs_access_masks[];
+			access_mask_t fs_access_masks[];
 		};
 	};
 };
 
-struct landlock_ruleset *landlock_create_ruleset(const u32 fs_access_mask);
+struct landlock_ruleset *
+landlock_create_ruleset(const access_mask_t fs_access_mask);
 
 void landlock_put_ruleset(struct landlock_ruleset *const ruleset);
 void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset);
 
 int landlock_insert_rule(struct landlock_ruleset *const ruleset,
-		struct landlock_object *const object, const u32 access);
+			 struct landlock_object *const object,
+			 const access_mask_t access);
 
-struct landlock_ruleset *landlock_merge_ruleset(
-		struct landlock_ruleset *const parent,
-		struct landlock_ruleset *const ruleset);
+struct landlock_ruleset *
+landlock_merge_ruleset(struct landlock_ruleset *const parent,
+		       struct landlock_ruleset *const ruleset);
 
-const struct landlock_rule *landlock_find_rule(
-		const struct landlock_ruleset *const ruleset,
-		const struct landlock_object *const object);
+const struct landlock_rule *
+landlock_find_rule(const struct landlock_ruleset *const ruleset,
+		   const struct landlock_object *const object);
 
 static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset)
 {
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index 7e27ce394020..735a0865ea11 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -43,9 +43,10 @@
  * @src: User space pointer or NULL.
  * @usize: (Alleged) size of the data pointed to by @src.
  */
-static __always_inline int copy_min_struct_from_user(void *const dst,
-		const size_t ksize, const size_t ksize_min,
-		const void __user *const src, const size_t usize)
+static __always_inline int
+copy_min_struct_from_user(void *const dst, const size_t ksize,
+			  const size_t ksize_min, const void __user *const src,
+			  const size_t usize)
 {
 	/* Checks buffer inconsistencies. */
 	BUILD_BUG_ON(!dst);
@@ -93,7 +94,7 @@ static void build_check_abi(void)
 /* Ruleset handling */
 
 static int fop_ruleset_release(struct inode *const inode,
-		struct file *const filp)
+			       struct file *const filp)
 {
 	struct landlock_ruleset *ruleset = filp->private_data;
 
@@ -102,15 +103,15 @@ static int fop_ruleset_release(struct inode *const inode,
 }
 
 static ssize_t fop_dummy_read(struct file *const filp, char __user *const buf,
-		const size_t size, loff_t *const ppos)
+			      const size_t size, loff_t *const ppos)
 {
 	/* Dummy handler to enable FMODE_CAN_READ. */
 	return -EINVAL;
 }
 
 static ssize_t fop_dummy_write(struct file *const filp,
-		const char __user *const buf, const size_t size,
-		loff_t *const ppos)
+			       const char __user *const buf, const size_t size,
+			       loff_t *const ppos)
 {
 	/* Dummy handler to enable FMODE_CAN_WRITE. */
 	return -EINVAL;
@@ -128,7 +129,7 @@ static const struct file_operations ruleset_fops = {
 	.write = fop_dummy_write,
 };
 
-#define LANDLOCK_ABI_VERSION	1
+#define LANDLOCK_ABI_VERSION 2
 
 /**
  * sys_landlock_create_ruleset - Create a new ruleset
@@ -168,22 +169,23 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
 		return -EOPNOTSUPP;
 
 	if (flags) {
-		if ((flags == LANDLOCK_CREATE_RULESET_VERSION)
-				&& !attr && !size)
+		if ((flags == LANDLOCK_CREATE_RULESET_VERSION) && !attr &&
+		    !size)
 			return LANDLOCK_ABI_VERSION;
 		return -EINVAL;
 	}
 
 	/* Copies raw user space buffer. */
 	err = copy_min_struct_from_user(&ruleset_attr, sizeof(ruleset_attr),
-			offsetofend(typeof(ruleset_attr), handled_access_fs),
-			attr, size);
+					offsetofend(typeof(ruleset_attr),
+						    handled_access_fs),
+					attr, size);
 	if (err)
 		return err;
 
 	/* Checks content (and 32-bits cast). */
 	if ((ruleset_attr.handled_access_fs | LANDLOCK_MASK_ACCESS_FS) !=
-			LANDLOCK_MASK_ACCESS_FS)
+	    LANDLOCK_MASK_ACCESS_FS)
 		return -EINVAL;
 
 	/* Checks arguments and transforms to kernel struct. */
@@ -193,7 +195,7 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
 
 	/* Creates anonymous FD referring to the ruleset. */
 	ruleset_fd = anon_inode_getfd("[landlock-ruleset]", &ruleset_fops,
-			ruleset, O_RDWR | O_CLOEXEC);
+				      ruleset, O_RDWR | O_CLOEXEC);
 	if (ruleset_fd < 0)
 		landlock_put_ruleset(ruleset);
 	return ruleset_fd;
@@ -204,7 +206,7 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
  * landlock_put_ruleset() on the return value.
  */
 static struct landlock_ruleset *get_ruleset_from_fd(const int fd,
-		const fmode_t mode)
+						    const fmode_t mode)
 {
 	struct fd ruleset_f;
 	struct landlock_ruleset *ruleset;
@@ -244,8 +246,8 @@ static int get_path_from_fd(const s32 fd, struct path *const path)
 	struct fd f;
 	int err = 0;
 
-	BUILD_BUG_ON(!__same_type(fd,
-		((struct landlock_path_beneath_attr *)NULL)->parent_fd));
+	BUILD_BUG_ON(!__same_type(
+		fd, ((struct landlock_path_beneath_attr *)NULL)->parent_fd));
 
 	/* Handles O_PATH. */
 	f = fdget_raw(fd);
@@ -257,10 +259,10 @@ static int get_path_from_fd(const s32 fd, struct path *const path)
 	 * pipefs).
 	 */
 	if ((f.file->f_op == &ruleset_fops) ||
-			(f.file->f_path.mnt->mnt_flags & MNT_INTERNAL) ||
-			(f.file->f_path.dentry->d_sb->s_flags & SB_NOUSER) ||
-			d_is_negative(f.file->f_path.dentry) ||
-			IS_PRIVATE(d_backing_inode(f.file->f_path.dentry))) {
+	    (f.file->f_path.mnt->mnt_flags & MNT_INTERNAL) ||
+	    (f.file->f_path.dentry->d_sb->s_flags & SB_NOUSER) ||
+	    d_is_negative(f.file->f_path.dentry) ||
+	    IS_PRIVATE(d_backing_inode(f.file->f_path.dentry))) {
 		err = -EBADFD;
 		goto out_fdput;
 	}
@@ -290,19 +292,18 @@ out_fdput:
  *
  * - EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time;
  * - EINVAL: @flags is not 0, or inconsistent access in the rule (i.e.
- *   &landlock_path_beneath_attr.allowed_access is not a subset of the rule's
- *   accesses);
+ *   &landlock_path_beneath_attr.allowed_access is not a subset of the
+ *   ruleset handled accesses);
  * - ENOMSG: Empty accesses (e.g. &landlock_path_beneath_attr.allowed_access);
  * - EBADF: @ruleset_fd is not a file descriptor for the current thread, or a
  *   member of @rule_attr is not a file descriptor as expected;
  * - EBADFD: @ruleset_fd is not a ruleset file descriptor, or a member of
- *   @rule_attr is not the expected file descriptor type (e.g. file open
- *   without O_PATH);
+ *   @rule_attr is not the expected file descriptor type;
  * - EPERM: @ruleset_fd has no write access to the underlying ruleset;
  * - EFAULT: @rule_attr inconsistency.
  */
-SYSCALL_DEFINE4(landlock_add_rule,
-		const int, ruleset_fd, const enum landlock_rule_type, rule_type,
+SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
+		const enum landlock_rule_type, rule_type,
 		const void __user *const, rule_attr, const __u32, flags)
 {
 	struct landlock_path_beneath_attr path_beneath_attr;
@@ -317,20 +318,24 @@ SYSCALL_DEFINE4(landlock_add_rule,
 	if (flags)
 		return -EINVAL;
 
-	if (rule_type != LANDLOCK_RULE_PATH_BENEATH)
-		return -EINVAL;
-
-	/* Copies raw user space buffer, only one type for now. */
-	res = copy_from_user(&path_beneath_attr, rule_attr,
-			sizeof(path_beneath_attr));
-	if (res)
-		return -EFAULT;
-
 	/* Gets and checks the ruleset. */
 	ruleset = get_ruleset_from_fd(ruleset_fd, FMODE_CAN_WRITE);
 	if (IS_ERR(ruleset))
 		return PTR_ERR(ruleset);
 
+	if (rule_type != LANDLOCK_RULE_PATH_BENEATH) {
+		err = -EINVAL;
+		goto out_put_ruleset;
+	}
+
+	/* Copies raw user space buffer, only one type for now. */
+	res = copy_from_user(&path_beneath_attr, rule_attr,
+			     sizeof(path_beneath_attr));
+	if (res) {
+		err = -EFAULT;
+		goto out_put_ruleset;
+	}
+
 	/*
 	 * Informs about useless rule: empty allowed_access (i.e. deny rules)
 	 * are ignored in path walks.
@@ -344,7 +349,7 @@ SYSCALL_DEFINE4(landlock_add_rule,
 	 * (ruleset->fs_access_masks[0] is automatically upgraded to 64-bits).
 	 */
 	if ((path_beneath_attr.allowed_access | ruleset->fs_access_masks[0]) !=
-			ruleset->fs_access_masks[0]) {
+	    ruleset->fs_access_masks[0]) {
 		err = -EINVAL;
 		goto out_put_ruleset;
 	}
@@ -356,7 +361,7 @@ SYSCALL_DEFINE4(landlock_add_rule,
 
 	/* Imports the new rule. */
 	err = landlock_append_fs_rule(ruleset, &path,
-			path_beneath_attr.allowed_access);
+				      path_beneath_attr.allowed_access);
 	path_put(&path);
 
 out_put_ruleset:
@@ -389,8 +394,8 @@ out_put_ruleset:
  * - E2BIG: The maximum number of stacked rulesets is reached for the current
  *   thread.
  */
-SYSCALL_DEFINE2(landlock_restrict_self,
-		const int, ruleset_fd, const __u32, flags)
+SYSCALL_DEFINE2(landlock_restrict_self, const int, ruleset_fd, const __u32,
+		flags)
 {
 	struct landlock_ruleset *new_dom, *ruleset;
 	struct cred *new_cred;
@@ -400,18 +405,18 @@ SYSCALL_DEFINE2(landlock_restrict_self,
 	if (!landlock_initialized)
 		return -EOPNOTSUPP;
 
-	/* No flag for now. */
-	if (flags)
-		return -EINVAL;
-
 	/*
 	 * Similar checks as for seccomp(2), except that an -EPERM may be
 	 * returned.
 	 */
 	if (!task_no_new_privs(current) &&
-			!ns_capable_noaudit(current_user_ns(), CAP_SYS_ADMIN))
+	    !ns_capable_noaudit(current_user_ns(), CAP_SYS_ADMIN))
 		return -EPERM;
 
+	/* No flag for now. */
+	if (flags)
+		return -EINVAL;
+
 	/* Gets and checks the ruleset. */
 	ruleset = get_ruleset_from_fd(ruleset_fd, FMODE_CAN_READ);
 	if (IS_ERR(ruleset))
diff --git a/security/security.c b/security/security.c
index 99956d2d29e1..188b8f782220 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1198,15 +1198,8 @@ int security_path_rename(const struct path *old_dir, struct dentry *old_dentry,
 		     (d_is_positive(new_dentry) && IS_PRIVATE(d_backing_inode(new_dentry)))))
 		return 0;
 
-	if (flags & RENAME_EXCHANGE) {
-		int err = call_int_hook(path_rename, 0, new_dir, new_dentry,
-					old_dir, old_dentry);
-		if (err)
-			return err;
-	}
-
 	return call_int_hook(path_rename, 0, old_dir, old_dentry, new_dir,
-				new_dentry);
+				new_dentry, flags);
 }
 EXPORT_SYMBOL(security_path_rename);
 
diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c
index b6a31901f289..71e82d855ebf 100644
--- a/security/tomoyo/tomoyo.c
+++ b/security/tomoyo/tomoyo.c
@@ -264,17 +264,26 @@ static int tomoyo_path_link(struct dentry *old_dentry, const struct path *new_di
  * @old_dentry: Pointer to "struct dentry".
  * @new_parent: Pointer to "struct path".
  * @new_dentry: Pointer to "struct dentry".
+ * @flags: Rename options.
  *
  * Returns 0 on success, negative value otherwise.
  */
 static int tomoyo_path_rename(const struct path *old_parent,
 			      struct dentry *old_dentry,
 			      const struct path *new_parent,
-			      struct dentry *new_dentry)
+			      struct dentry *new_dentry,
+			      const unsigned int flags)
 {
 	struct path path1 = { .mnt = old_parent->mnt, .dentry = old_dentry };
 	struct path path2 = { .mnt = new_parent->mnt, .dentry = new_dentry };
 
+	if (flags & RENAME_EXCHANGE) {
+		const int err = tomoyo_path2_perm(TOMOYO_TYPE_RENAME, &path2,
+				&path1);
+
+		if (err)
+			return err;
+	}
 	return tomoyo_path2_perm(TOMOYO_TYPE_RENAME, &path1, &path2);
 }