[PATCH v7 00/10] Implement LANDLOCK_ADD_RULE_NO_INHERIT

[PATCH v7 00/10] Implement LANDLOCK_ADD_RULE_NO_INHERIT

[Justin Suess]

Hi,

This is version 7 of the LANDLOCK_ADD_RULE_NO_INHERIT series, which
implements a new flag to suppress inheritance of access rights and
flags from parent objects.

This version of the series focuses again on cleanup, splitting out
some patches and fixing an edge case with disconnected directories.

Behavior of the flag is identical to the previous patch.

This series is rebased on v8 of Tingmao Wang's "quiet flag" series.

Previous patch summary:

The new flag enables policies where a parent directory needs broader
access than its children. For example, a sandbox may permit read-write
access to /home/user but still prohibit writes to ~/.bashrc or
~/.ssh, even though they are nested beneath the parent. Today this is
not possible because access rights always propagate from parent to
child inodes.

When a rule is added with LANDLOCK_ADD_RULE_NO_INHERIT:

  * access rights on parent inodes are ignored for that inode and its
    descendants; and
  * operations that reparent, rename, or remove the tagged inode or
    its ancestors (via rename, rmdir, link) are denied up to the VFS
    root; and
  * parent flags do not propagate below a NO_INHERIT rule.

These parent-directory restrictions help mitigate sandbox-restart
attacks: a sandboxed process could otherwise move a protected
directory before exit, causing the next sandbox instance to apply its
policy to the wrong path.

Changes since v6:

  1. The main implementation of NO_INHERIT was split into smaller more
     reviewable patches, separating the landlock_walk_path_up
     implementation, usages of landlock_walk_path_up, and the find_rule
     move to separate patches
  2. A small issue regarding disconnected directory handling, where rules
     inserted with NO_INHERIT only had protection up to a disconnected
     directory instead of the mountpoint was fixed. In practice, this
     isn't a problem at the current time since landlock forbids the mount
     syscall needed to move a mountpoint with MS_MOVE. However, for
     future-proofing in the case landlock allows some mount operations,
     restrictions on parent directories now apply to the real root.

Changes since v5:

  1. Retain existing documentation for path traversal in
     is_access_to_paths_allowed.
  2. Change conditional for path walk in is_access_to_paths_allowed
     removing possibility of infinite loop and renamed constant.
  3. Remove (now) redundant mnt_root parameter from
     collect_domain_accesses.
  4. Change path parameter to a dentry for
     deny_no_inherit_topology_change because only the dentry was needed.
  5. Remove duplicated tree diagram comment from selftests.
  6. Minor documentation fixes.

  Credit to Tingmao Wang for pointing out 1, 2, 3, 4, and 6.

Changes since v4:

  1. Trimmed 120 lines from core implementation in fs.c.
  2. Centralized path traversal logic with a helper function
     landlock_walk_path_up.
  3. Fixed bug in test on applying LANDLOCK_ADD_RULE_NO_INHERIT on
     a file, giving it valid access rights.
  4. Restructured commits to allow independent builds.
  5. Adds userspace API documentation for the flag.

Changes since v3:

  1. Trimmed core implementation in fs.c by removing redundant functions.
  2. Fixed placement/inclusion of prototypes.
  3. Added 4 new selftests for bind mount cases.
  4. Protections now apply up to the VFS root instead of the mountpoint
     root.

Links:

v1:
  https://lore.kernel.org/linux-security-module/20251105180019.1432367-1-utilityemal77@gmail.com/
v2:
  https://lore.kernel.org/linux-security-module/20251120222346.1157004-1-utilityemal77@gmail.com/
v3:
  https://lore.kernel.org/linux-security-module/20251126122039.3832162-1-utilityemal77@gmail.com/
v4:
  https://lore.kernel.org/linux-security-module/20251207015132.800576-1-utilityemal77@gmail.com/
v5:
  https://lore.kernel.org/linux-security-module/20251214170548.408142-1-utilityemal77@gmail.com/
quiet-flag v6:
  https://lore.kernel.org/linux-security-module/cover.1765040503.git.m@maowtm.org/
quiet-flag v7:
  https://lore.kernel.org/linux-security-module/cover.1766330134.git.m@maowtm.org/
quiet-flag v8:
  https://lore.kernel.org/linux-security-module/cover.1775490344.git.m@maowtm.org/

Example usage:

  # LL_FS_RO="/a/b/c" LL_FS_RW="/" LL_FS_NO_INHERIT="/a/b/c"
    landlock-sandboxer sh
  # touch /a/b/c/fi                    # denied; / RW does not inherit
  # rmdir /a/b/c                       # denied by ancestor protections
  # mv /a /bad                         # denied
  # mkdir /a/good; touch /a/good/fi    # allowed; unrelated path

All tests added by this series, and all other existing landlock tests,
are passing. This patch was also validated through checkpatch.pl.

Special thanks to Tingmao Wang and Mickaël Salaün for your valuable
feedback.

Thank you for your time and review.

Regards,
Justin Suess

Justin Suess (10):
  landlock: Add path walk helper
  landlock: Use landlock_walk_path_up for is_access_to_paths_allowed
  landlock: Use landlock_walk_path_up for collect_domain_accesses
  landlock: Implement LANDLOCK_ADD_RULE_NO_INHERIT userspace api
  landlock: Move find_rule definition above landlock_append_fs_rule
  landlock: Implement LANDLOCK_ADD_RULE_NO_INHERIT
  landlock: Add documentation for LANDLOCK_ADD_RULE_NO_INHERIT
  samples/landlock: Add LANDLOCK_ADD_RULE_NO_INHERIT to
    landlock-sandboxer
  selftests/landlock: Implement selftests for
    LANDLOCK_ADD_RULE_NO_INHERIT
  landlock: Implement KUnit test for LANDLOCK_ADD_RULE_NO_INHERIT

 Documentation/userspace-api/landlock.rst   |  17 +
 include/uapi/linux/landlock.h              |  29 +-
 samples/landlock/sandboxer.c               |  11 +
 security/landlock/fs.c                     | 342 +++++++---
 security/landlock/ruleset.c                | 125 +++-
 security/landlock/ruleset.h                |  26 +
 security/landlock/syscalls.c               |  15 +-
 tools/testing/selftests/landlock/fs_test.c | 705 +++++++++++++++++++++
 8 files changed, 1151 insertions(+), 119 deletions(-)

-- 
2.53.0

[PATCH v7 01/10] landlock: Add path walk helper

[Justin Suess]

Add path walk helper landlock_walk_path_up. This helper takes a pointer
to a struct path and walks the path upward towards the VFS root, and
returns an enum corresponding whether the current position in the walk
is an internal mountpoint, the real root, or neither.

Cc: Tingmao Wang <m@maowtm.org>
Signed-off-by: Justin Suess <utilityemal77@gmail.com>
---

Notes:
    v6..v7 changes:
    
      * New patch split out from the v6 core NO_INHERIT implementation.
      * Added enum comments.

 security/landlock/fs.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index bd7554d0b65a..644637a8c0b5 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -320,6 +320,38 @@ static struct landlock_object *get_inode_object(struct inode *const inode)
 	LANDLOCK_ACCESS_FS_RESOLVE_UNIX)
 /* clang-format on */
 
+/**
+ * enum landlock_walk_result - Result codes for landlock_walk_path_up()
+ * @LANDLOCK_WALK_CONTINUE: Path is now neither the real root nor an internal mount point.
+ * @LANDLOCK_WALK_STOP_REAL_ROOT: Path has reached the real VFS root.
+ * @LANDLOCK_WALK_INTERNAL: Path has reached an internal mount point.
+ */
+enum landlock_walk_result {
+	LANDLOCK_WALK_CONTINUE,
+	LANDLOCK_WALK_STOP_REAL_ROOT,
+	LANDLOCK_WALK_INTERNAL,
+};
+
+static enum landlock_walk_result landlock_walk_path_up(struct path *const path)
+{
+	struct dentry *old;
+
+	while (path->dentry == path->mnt->mnt_root) {
+		if (!follow_up(path))
+			return LANDLOCK_WALK_STOP_REAL_ROOT;
+	}
+	old = path->dentry;
+	if (unlikely(IS_ROOT(old))) {
+		if (likely(path->mnt->mnt_flags & MNT_INTERNAL))
+			return LANDLOCK_WALK_INTERNAL;
+		path->dentry = dget(path->mnt->mnt_root);
+	} else {
+		path->dentry = dget_parent(old);
+	}
+	dput(old);
+	return LANDLOCK_WALK_CONTINUE;
+}
+
 /*
  * @path: Should have been checked by get_path_from_fd().
  */
-- 
2.53.0

[PATCH v7 02/10] landlock: Use landlock_walk_path_up for is_access_to_paths_allowed

[Justin Suess]

Use common path walk helper for is_access_to_paths_allowed. This
maintains consistency with the existing implementation, and removes the
backward goto jump.

Signed-off-by: Justin Suess <utilityemal77@gmail.com>
---

Notes:
    v6..v7 changes:
    
      * New patch split out from the v6 core NO_INHERIT implementation.

 security/landlock/fs.c | 60 ++++++++++++++----------------------------
 1 file changed, 20 insertions(+), 40 deletions(-)

diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 644637a8c0b5..b31bd2980e5c 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -923,47 +923,27 @@ static bool is_access_to_paths_allowed(
 		/* 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)) {
-				/* Ignores hidden mount points. */
-				goto jump_up;
-			} else {
-				/*
-				 * Stops at the real root.  Denies access
-				 * because not all layers have granted access.
-				 */
-				break;
-			}
-		}
-
-		if (unlikely(IS_ROOT(walker_path.dentry))) {
-			if (likely(walker_path.mnt->mnt_flags & MNT_INTERNAL)) {
-				/*
-				 * Stops and allows access when reaching disconnected root
-				 * directories that are part of internal filesystems (e.g. nsfs,
-				 * which is reachable through /proc/<pid>/ns/<namespace>).
-				 */
-				allowed_parent1 = true;
-				allowed_parent2 = true;
-				break;
-			}
-
-			/*
-			 * We reached a disconnected root directory from a bind mount.
-			 * Let's continue the walk with the mount point we missed.
-			 */
-			dput(walker_path.dentry);
-			walker_path.dentry = walker_path.mnt->mnt_root;
-			dget(walker_path.dentry);
-		} else {
-			struct dentry *const parent_dentry =
-				dget_parent(walker_path.dentry);
-
-			dput(walker_path.dentry);
-			walker_path.dentry = parent_dentry;
+		switch (landlock_walk_path_up(&walker_path)) {
+		/*
+		 * Stops and allows access when reaching disconnected root
+		 * directories that are part of internal filesystems (e.g. nsfs,
+		 * which is reachable through /proc/<pid>/ns/<namespace>).
+		 */
+		case LANDLOCK_WALK_INTERNAL:
+			allowed_parent1 = true;
+			allowed_parent2 = true;
+			break;
+		/*
+		 * Stops at the real root.  Denies access
+		 * because not all layers have granted access
+		 */
+		case LANDLOCK_WALK_STOP_REAL_ROOT:
+			break;
+		/* Otherwise, keep walking up to the root. */
+		case LANDLOCK_WALK_CONTINUE:
+			continue;
 		}
+		break;
 	}
 	path_put(&walker_path);
 
-- 
2.53.0

[PATCH v7 03/10] landlock: Use landlock_walk_path_up for collect_domain_accesses

[Justin Suess]

Use common path walk helper for collect_domain_accesses. This
extends the new centralized traversal logic to the current_check_refer
path code flow, and maintains consistency with the is_access_to_paths
allowed traversal while allowing reuse of traversal semantics.

Signed-off-by: Justin Suess <utilityemal77@gmail.com>
---

Notes:
    v6..v7 changes:
    
      * New patch split out from the v6 core NO_INHERIT implementation.

 security/landlock/fs.c | 75 ++++++++++++++++++++++--------------------
 1 file changed, 40 insertions(+), 35 deletions(-)

diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index b31bd2980e5c..7ec26c671f91 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -1036,49 +1036,52 @@ static access_mask_t maybe_remove(const struct dentry *const dentry)
  * 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.
+ * @path: Path to start the walk from and whose mount root is the last
+ *     directory to check.
  * @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 helper is useful to begin a path walk from @path to the mount 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 @path to that mount root, we record all the domain's allowed
+ * accesses in @layer_masks_dom.
  *
- * Because of disconnected directories, this walk may not reach @mnt_dir.  In
- * this case, the walk will continue to @mnt_dir after this call.
+ * Because of disconnected directories, this walk may not reach that mount
+ * root.  In this case, the walk will continue to the mount root after this
+ * call.
  *
  * This is similar to is_access_to_paths_allowed() but much simpler because it
  * only handles walking on the same mount point and only checks one set of
  * accesses.
  *
- * Return: True if all the domain access rights are allowed for @dir, false if
- * the walk reached @mnt_root.
+ * Return: True if all the domain access rights are allowed for @path, false if
+ * the walk reached the mount root.
  */
 static bool
 collect_domain_accesses(const struct landlock_ruleset *const domain,
-			const struct dentry *const mnt_root, struct dentry *dir,
+			const struct path *const path,
 			struct layer_access_masks *layer_masks_dom,
 			struct collected_rule_flags *const rule_flags)
 {
 	bool ret = false;
+	struct path walker_path;
 
-	if (WARN_ON_ONCE(!domain || !mnt_root || !dir || !layer_masks_dom))
+	if (WARN_ON_ONCE(!domain || !path || !path->dentry ||
+			 !path->mnt || !layer_masks_dom))
 		return true;
-	if (is_nouser_or_private(dir))
+	if (is_nouser_or_private(path->dentry))
 		return true;
 
 	if (!landlock_init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
 				       layer_masks_dom, LANDLOCK_KEY_INODE))
 		return true;
 
-	dget(dir);
+	walker_path = *path;
+	path_get(&walker_path);
 	while (true) {
-		struct dentry *parent_dentry;
-
 		/* Gets all layers allowing all domain accesses. */
-		if (landlock_unmask_layers(find_rule(domain, dir),
+		if (landlock_unmask_layers(find_rule(domain,
+						     walker_path.dentry),
 					   layer_masks_dom, rule_flags)) {
 			/*
 			 * Stops when all handled accesses are allowed by at
@@ -1092,14 +1095,16 @@ collect_domain_accesses(const struct landlock_ruleset *const domain,
 		 * Stops at the mount point or the filesystem root for a disconnected
 		 * directory.
 		 */
-		if (dir == mnt_root || unlikely(IS_ROOT(dir)))
+		if ((walker_path.dentry == path->mnt->mnt_root &&
+		     walker_path.mnt == path->mnt) ||
+		    unlikely(IS_ROOT(walker_path.dentry)))
 			break;
 
-		parent_dentry = dget_parent(dir);
-		dput(dir);
-		dir = parent_dentry;
+		if (WARN_ON_ONCE(landlock_walk_path_up(&walker_path) !=
+				 LANDLOCK_WALK_CONTINUE))
+			break;
 	}
-	dput(dir);
+	path_put(&walker_path);
 	return ret;
 }
 
@@ -1165,7 +1170,7 @@ static int current_check_refer_path(struct dentry *const old_dentry,
 	bool allow_parent1, allow_parent2;
 	access_mask_t access_request_parent1, access_request_parent2;
 	struct path mnt_dir;
-	struct dentry *old_parent;
+	struct path old_parent_path;
 	struct layer_access_masks layer_masks_parent1 = {},
 				  layer_masks_parent2 = {};
 	struct landlock_request request1 = {}, request2 = {};
@@ -1223,19 +1228,19 @@ static int current_check_refer_path(struct dentry *const old_dentry,
 	/*
 	 * old_dentry may be the root of the common mount point and
 	 * !IS_ROOT(old_dentry) at the same time (e.g. with open_tree() and
-	 * OPEN_TREE_CLONE).  We do not need to call dget(old_parent) because
-	 * we keep a reference to old_dentry.
+	 * OPEN_TREE_CLONE).  We do not need to call path_get(&old_parent_path)
+	 * because we keep a reference to old_dentry.
 	 */
-	old_parent = (old_dentry == mnt_dir.dentry) ? old_dentry :
-						      old_dentry->d_parent;
+	old_parent_path.mnt = mnt_dir.mnt;
+	old_parent_path.dentry = (old_dentry == mnt_dir.dentry) ?
+					 old_dentry :
+					 old_dentry->d_parent;
 
 	/* new_dir->dentry is equal to new_dentry->d_parent */
-	allow_parent1 = collect_domain_accesses(subject->domain, mnt_dir.dentry,
-						old_parent,
-						&layer_masks_parent1,
-						&rule_flags_parent1);
-	allow_parent2 = collect_domain_accesses(subject->domain, mnt_dir.dentry,
-						new_dir->dentry,
+	allow_parent1 = collect_domain_accesses(
+		subject->domain, &old_parent_path,
+		&layer_masks_parent1, &rule_flags_parent1);
+	allow_parent2 = collect_domain_accesses(subject->domain, new_dir,
 						&layer_masks_parent2,
 						&rule_flags_parent2);
 	if (allow_parent1 && allow_parent2)
@@ -1256,7 +1261,7 @@ static int current_check_refer_path(struct dentry *const old_dentry,
 		return 0;
 
 	if (request1.access) {
-		request1.audit.u.path.dentry = old_parent;
+		request1.audit.u.path.dentry = old_parent_path.dentry;
 		request1.rule_flags = rule_flags_parent1;
 		landlock_log_denial(subject, &request1);
 	}
-- 
2.53.0

[PATCH v7 04/10] landlock: Implement LANDLOCK_ADD_RULE_NO_INHERIT userspace api

[Justin Suess]

Implements the syscall side flag handling and kernel api headers for the
LANDLOCK_ADD_RULE_NO_INHERIT flag.

Signed-off-by: Justin Suess <utilityemal77@gmail.com>
---

Notes:
    v6..v7 changes:
    
      * None
    
    v5..v6 changes:
    
      * None
    
    v4..v5 changes:
    
      * Moved syscall handling to this patch and moved out flag definition
        to allow independent build.
    
    v3..v4 changes:
    
      * Changed documentation to reflect protections now apply to VFS root
        instead of the mountpoint.
    
    v2..v3 changes:
    
      * Extended documentation for flag inheritance suppression on
        LANDLOCK_ADD_RULE_NO_INHERIT.
      * Extended the flag validation rules in the syscall.
      * Added mention of no inherit in empty rules in add_rule_path_beneath
        as per Tingmao Wang's suggestion.
      * Added check for useless no-inherit flag in networking rules.

 include/uapi/linux/landlock.h | 29 ++++++++++++++++++++++++++++-
 security/landlock/syscalls.c  | 15 +++++++++++----
 2 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
index 9a41c65623a1..290f76774e3f 100644
--- a/include/uapi/linux/landlock.h
+++ b/include/uapi/linux/landlock.h
@@ -127,10 +127,37 @@ struct landlock_ruleset_attr {
  *     allowed_access in the passed in rule_attr.  When this flag is
  *     present, the caller is also allowed to pass in an empty
  *     allowed_access.
+ * %LANDLOCK_ADD_RULE_NO_INHERIT
+ *     When set on a rule being added to a ruleset, this flag disables the
+ *     inheritance of access rights and flags from parent objects.
+ *
+ *     This flag currently applies only to filesystem rules.  Adding it to
+ *     non-filesystem rules will return -EINVAL, unless future extensions
+ *     of Landlock define other hierarchical object types.
+ *
+ *     By default, Landlock filesystem rules inherit allowed accesses from
+ *     ancestor directories: if a parent directory grants certain rights,
+ *     those rights also apply to its children.  A rule marked with
+ *     LANDLOCK_ADD_RULE_NO_INHERIT stops this propagation at the directory
+ *     covered by the rule.  Descendants of that directory continue to inherit
+ *     normally unless they also have rules using this flag.
+ *
+ *     If a regular file is marked with this flag, it will not inherit any
+ *     access rights from its parent directories; only the accesses explicitly
+ *     allowed by the rule will apply to that file.
+ *
+ *     This flag also enforces parent-directory restrictions: rename, rmdir,
+ *     link, and other operations that would change the directory's immediate
+ *     parent subtree are denied up to the VFS root.  This prevents
+ *     sandboxed processes from manipulating the filesystem hierarchy to evade
+ *     restrictions (e.g., via sandbox-restart attacks).
+ *
+ *     In addition, this flag blocks the inheritance of rule flags from parent
+ *     directories to the object covered by this rule.
  */
-
 /* clang-format off */
 #define LANDLOCK_ADD_RULE_QUIET			(1U << 0)
+#define LANDLOCK_ADD_RULE_NO_INHERIT		(1U << 1)
 /* clang-format on */
 
 /**
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index a71068c41f76..fbab6573df70 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -360,7 +360,7 @@ static int add_rule_path_beneath(struct landlock_ruleset *const ruleset,
 	/*
 	 * Informs about useless rule: empty allowed_access (i.e. deny rules)
 	 * are ignored in path walks.  However, the rule is not useless if it
-	 * is there to hold a quiet flag
+	 * is there to hold a quiet or no inherit flag
 	 */
 	if (!flags && !path_beneath_attr.allowed_access)
 		return -ENOMSG;
@@ -414,6 +414,9 @@ static int add_rule_net_port(struct landlock_ruleset *ruleset,
 	/* Check for useless quiet flag. */
 	if (flags & LANDLOCK_ADD_RULE_QUIET && !ruleset->quiet_masks.net)
 		return -EINVAL;
+	/* No inherit is always useless for this scope */
+	if (flags & LANDLOCK_ADD_RULE_NO_INHERIT)
+		return -EINVAL;
 
 	/* Denies inserting a rule with port greater than 65535. */
 	if (net_port_attr.port > U16_MAX)
@@ -432,7 +435,7 @@ static int add_rule_net_port(struct landlock_ruleset *ruleset,
  * @rule_type: Identify the structure type pointed to by @rule_attr:
  *             %LANDLOCK_RULE_PATH_BENEATH or %LANDLOCK_RULE_NET_PORT.
  * @rule_attr: Pointer to a rule (matching the @rule_type).
- * @flags: Must be 0 or %LANDLOCK_ADD_RULE_QUIET.
+ * @flags: Must be 0 or %LANDLOCK_ADD_RULE_QUIET or %LANDLOCK_ADD_RULE_NO_INHERIT.
  *
  * This system call enables to define a new rule and add it to an existing
  * ruleset.
@@ -470,8 +473,12 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
 
 	if (!is_initialized())
 		return -EOPNOTSUPP;
-
-	if (flags && flags != LANDLOCK_ADD_RULE_QUIET)
+	/* Checks flag existence */
+	if (flags & ~(LANDLOCK_ADD_RULE_NO_INHERIT | LANDLOCK_ADD_RULE_QUIET))
+		return -EINVAL;
+	/* No inherit may only apply on path_beneath rules. */
+	if ((flags & LANDLOCK_ADD_RULE_NO_INHERIT) &&
+	    rule_type != LANDLOCK_RULE_PATH_BENEATH)
 		return -EINVAL;
 
 	/* Gets and checks the ruleset. */
-- 
2.53.0

[PATCH v7 05/10] landlock: Move find_rule definition above landlock_append_fs_rule

[Justin Suess]

Move find_rule above landlock_append_fs_rule to allow usage of find_rule
from within without an additional prototype declaration

Cc: Tingmao Wang <m@maowtm.org>
Signed-off-by: Justin Suess <utilityemal77@gmail.com>
---

Notes:
    v6..v7 changes:
    
      * New patch split out from the v6 core NO_INHERIT implementation.

 security/landlock/fs.c | 58 +++++++++++++++++++++---------------------
 1 file changed, 29 insertions(+), 29 deletions(-)

diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 7ec26c671f91..86a3435ebbba 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -352,6 +352,35 @@ static enum landlock_walk_result landlock_walk_path_up(struct path *const path)
 	return LANDLOCK_WALK_CONTINUE;
 }
 
+/* Access-control management */
+
+/*
+ * The lifetime of the returned rule is tied to @domain.
+ *
+ * Returns NULL if no rule is found or if @dentry is negative.
+ */
+static 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;
+	struct landlock_id id = {
+		.type = LANDLOCK_KEY_INODE,
+	};
+
+	/* Ignores nonexistent leafs. */
+	if (d_is_negative(dentry))
+		return NULL;
+
+	inode = d_backing_inode(dentry);
+	rcu_read_lock();
+	id.key.object = rcu_dereference(landlock_inode(inode)->object);
+	rule = landlock_find_rule(domain, id);
+	rcu_read_unlock();
+	return rule;
+}
+
 /*
  * @path: Should have been checked by get_path_from_fd().
  */
@@ -388,35 +417,6 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
 	return err;
 }
 
-/* Access-control management */
-
-/*
- * The lifetime of the returned rule is tied to @domain.
- *
- * Returns NULL if no rule is found or if @dentry is negative.
- */
-static 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;
-	struct landlock_id id = {
-		.type = LANDLOCK_KEY_INODE,
-	};
-
-	/* Ignores nonexistent leafs. */
-	if (d_is_negative(dentry))
-		return NULL;
-
-	inode = d_backing_inode(dentry);
-	rcu_read_lock();
-	id.key.object = rcu_dereference(landlock_inode(inode)->object);
-	rule = landlock_find_rule(domain, id);
-	rcu_read_unlock();
-	return rule;
-}
-
 /*
  * Allows access to pseudo filesystems that will never be mountable (e.g.
  * sockfs, pipefs), but can still be reachable through
-- 
2.53.0

[PATCH v7 06/10] landlock: Implement LANDLOCK_ADD_RULE_NO_INHERIT

[Justin Suess]

Implements a flag to prevent access grant inheritance within the filesystem
hierarchy for landlock rules.

If a landlock rule on an inode has this flag, any access grants on parent
inodes will be ignored. Moreover, operations that involve altering the
ancestors of the subject with LANDLOCK_ADD_RULE_NO_INHERIT will be
denied up to the VFS root.

Signed-off-by: Justin Suess <utilityemal77@gmail.com>
---

Notes:
    v6..v7 changes:
    
      * Split landlock_walk_path_up, the is_access_to_paths_allowed conversion,
        the collect_domain_accesses conversion, and the find_rule move into
        separate preparatory patches.
      * Fixed disconnected-directory handling in landlock_append_fs_rule() when
        marking NO_INHERIT ancestors.
    
    v5..v6 changes:
    
      * Retain existing documentation for path traversal in
        is_access_to_paths_allowed.
      * Change conditional for path walk in is_access_to_paths_allowed
        removing possibility of infinite loop and renamed constant.
      * Remove (now) redundant mnt_root parameter from
        collect_domain_accesses.
      * Change path parameter to a dentry for
        deny_no_inherit_topology_change because only the dentry was needed.
      * Minor documentation fixes.
    
    v4..v5 changes:
    
      * Centralized path walking logic with landlock_walk_path_up.
      * Removed redundant functions in fs.c, and streamlined core
        logic, removing ~120 lines of code.
      * Removed mark_no_inherit_ancestors, replacing with direct flag
        setting in append_fs_rule.
      * Removed micro-optimization of skipping ancestor processing
        when all layers have no_inherit, as it complicated the code
        significantly for little gain.
    
    v3..v4 changes:
    
      * Rebased on v6 of Tingmao Wang's quiet flag series.
      * Removed unnecessary mask_no_inherit_descendant_layers and related
        code at Tingmao Wang's suggestion, simplifying patch.
      * Updated to use new disconnected directory handling.
      * Improved WARN_ON_ONCE usage.
      * Removed redundant loop for single-layer rulesets.
      * Protections now apply up to the VFS root, not just the mountpoint.
      * Indentation fixes.
      * Removed redundant flag marker blocked_flag_masks.
    
    v2..v3 changes:
    
      * Parent directory topology protections now work by lazily
        inserting blank rules on parent inodes if they do not
        exist. This replaces the previous xarray implementation
        with simplified logic.
      * Added an optimization to skip further processing if all layers
        collected have no inherit.
      * Added support to block flag inheritance.

 security/landlock/fs.c      | 117 ++++++++++++++++++++++++++++++++++++
 security/landlock/ruleset.c |  40 +++++++++---
 security/landlock/ruleset.h |  26 ++++++++
 3 files changed, 173 insertions(+), 10 deletions(-)

diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 86a3435ebbba..6af1043a941f 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -392,6 +392,7 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
 	struct landlock_id id = {
 		.type = LANDLOCK_KEY_INODE,
 	};
+	struct path walker = *path;
 
 	/* Files only get access rights that make sense. */
 	if (!d_is_dir(path->dentry) &&
@@ -406,8 +407,44 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
 	id.key.object = get_inode_object(d_backing_inode(path->dentry));
 	if (IS_ERR(id.key.object))
 		return PTR_ERR(id.key.object);
+
 	mutex_lock(&ruleset->lock);
 	err = landlock_insert_rule(ruleset, id, access_rights, flags);
+	if (err || !(flags & LANDLOCK_ADD_RULE_NO_INHERIT))
+		goto out_unlock;
+
+	path_get(&walker);
+	while (landlock_walk_path_up(&walker) != LANDLOCK_WALK_STOP_REAL_ROOT) {
+		struct landlock_rule *ancestor_rule;
+
+		ancestor_rule = (struct landlock_rule *)find_rule(
+			ruleset, walker.dentry);
+		if (!ancestor_rule) {
+			struct landlock_id ancestor_id = {
+				.type = LANDLOCK_KEY_INODE,
+				.key.object = get_inode_object(
+					d_backing_inode(walker.dentry)),
+			};
+
+			if (IS_ERR(ancestor_id.key.object)) {
+				err = PTR_ERR(ancestor_id.key.object);
+				break;
+			}
+			/* Insert a "blank" rule for the ancestor. */
+			err = landlock_insert_rule(ruleset, ancestor_id, 0, 0);
+			landlock_put_object(ancestor_id.key.object);
+			if (err)
+				break;
+
+			ancestor_rule = (struct landlock_rule *)find_rule(
+				ruleset, walker.dentry);
+		}
+		/* Marks the ancestor rule, whether we inserted it or found it. */
+		ancestor_rule->layers[0].flags.has_no_inherit_descendant = true;
+	}
+	path_put(&walker);
+
+out_unlock:
 	mutex_unlock(&ruleset->lock);
 	/*
 	 * No need to check for an error because landlock_insert_rule()
@@ -1108,6 +1145,57 @@ collect_domain_accesses(const struct landlock_ruleset *const domain,
 	return ret;
 }
 
+/**
+ * deny_no_inherit_topology_change - deny topology changes on sealed paths
+ * @subject: Subject performing the operation (contains the domain).
+ * @path: Path whose dentry is the target of the topology modification.
+ *
+ * Checks whether any domain layers are sealed against topology changes at
+ * @path.  If so, emit an audit record and return -EACCES.  Otherwise return 0.
+ */
+static int
+deny_no_inherit_topology_change(const struct landlock_cred_security *subject,
+				struct dentry *const dcache_entry)
+{
+	layer_mask_t sealed_layers = 0;
+	layer_mask_t override_layers = 0;
+	const struct landlock_rule *rule;
+	size_t layer_index;
+
+	if (WARN_ON_ONCE(!subject || !dcache_entry ||
+			 d_is_negative(dcache_entry)))
+		return 0;
+
+	rule = find_rule(subject->domain, dcache_entry);
+	if (!rule)
+		return 0;
+
+	for (layer_index = 0; layer_index < rule->num_layers; layer_index++) {
+		const struct landlock_layer *layer = &rule->layers[layer_index];
+		layer_mask_t layer_bit = BIT_ULL(layer->level - 1);
+
+		if (layer->flags.no_inherit ||
+		    layer->flags.has_no_inherit_descendant)
+			sealed_layers |= layer_bit;
+		else
+			override_layers |= layer_bit;
+	}
+
+	sealed_layers &= ~override_layers;
+	if (!sealed_layers)
+		return 0;
+
+	landlock_log_denial(subject, &(struct landlock_request) {
+		.type = LANDLOCK_REQUEST_FS_CHANGE_TOPOLOGY,
+		.audit = {
+			.type = LSM_AUDIT_DATA_DENTRY,
+			.u.dentry = dcache_entry,
+		},
+		.layer_plus_one = __ffs((unsigned long)sealed_layers) + 1,
+	});
+	return -EACCES;
+}
+
 /**
  * current_check_refer_path - Check if a rename or link action is allowed
  *
@@ -1193,6 +1281,16 @@ static int current_check_refer_path(struct dentry *const old_dentry,
 	access_request_parent2 =
 		get_mode_access(d_backing_inode(old_dentry)->i_mode);
 	if (removable) {
+		int err = deny_no_inherit_topology_change(subject, old_dentry);
+
+		if (err)
+			return err;
+		if (exchange) {
+			err = deny_no_inherit_topology_change(subject,
+							      new_dentry);
+			if (err)
+				return err;
+		}
 		access_request_parent1 |= maybe_remove(old_dentry);
 		access_request_parent2 |= maybe_remove(new_dentry);
 	}
@@ -1589,12 +1687,31 @@ static int hook_path_symlink(const struct path *const dir,
 static int hook_path_unlink(const struct path *const dir,
 			    struct dentry *const dentry)
 {
+	const struct landlock_cred_security *const subject =
+		landlock_get_applicable_subject(current_cred(), any_fs, NULL);
+	int err;
+
+	if (subject) {
+		err = deny_no_inherit_topology_change(subject, dentry);
+		if (err)
+			return err;
+	}
 	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)
 {
+	const struct landlock_cred_security *const subject =
+		landlock_get_applicable_subject(current_cred(), any_fs, NULL);
+	int err;
+
+	if (subject) {
+		err = deny_no_inherit_topology_change(subject, dentry);
+		if (err)
+			return err;
+	}
+
 	return current_check_access_path(dir, LANDLOCK_ACCESS_FS_REMOVE_DIR);
 }
 
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index d2d1e3fb6cf2..8fdba3a7f983 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -257,6 +257,10 @@ static int insert_rule(struct landlock_ruleset *const ruleset,
 				return -EINVAL;
 			this->layers[0].access |= (*layers)[0].access;
 			this->layers[0].flags.quiet |= (*layers)[0].flags.quiet;
+			this->layers[0].flags.no_inherit |=
+				(*layers)[0].flags.no_inherit;
+			this->layers[0].flags.has_no_inherit_descendant |=
+				(*layers)[0].flags.has_no_inherit_descendant;
 			return 0;
 		}
 
@@ -309,14 +313,17 @@ int landlock_insert_rule(struct landlock_ruleset *const ruleset,
 			 const struct landlock_id id,
 			 const access_mask_t access, const int flags)
 {
-	struct landlock_layer layers[] = { {
-		.access = access,
-		/* When @level is zero, insert_rule() extends @ruleset. */
-		.level = 0,
-		.flags = {
-			.quiet = !!(flags & LANDLOCK_ADD_RULE_QUIET),
-		},
-	} };
+	struct landlock_layer layers
+		[] = { { .access = access,
+			 /* When @level is zero, insert_rule() extends @ruleset. */
+			 .level = 0,
+			 .flags = {
+				 .quiet = !!(flags & LANDLOCK_ADD_RULE_QUIET),
+				 .no_inherit = !!(flags &
+						  LANDLOCK_ADD_RULE_NO_INHERIT),
+				 .has_no_inherit_descendant = !!(
+					 flags & LANDLOCK_ADD_RULE_NO_INHERIT),
+			 } } };
 
 	build_check_layer();
 	return insert_rule(ruleset, id, &layers, ARRAY_SIZE(layers));
@@ -660,12 +667,25 @@ bool landlock_unmask_layers(const struct landlock_rule *const rule,
 		const struct landlock_layer *const layer = &rule->layers[i];
 		const layer_mask_t layer_bit = BIT_ULL(layer->level - 1);
 
+		/*
+		 * Skip layers that already have no_inherit set - these layers
+		 * should not inherit access rights from ancestor directories.
+		 */
+		if (rule_flags && (rule_flags->no_inherit_masks & layer_bit))
+			continue;
+
 		/* Clear the bits where the layer in the rule grants access. */
 		masks->access[layer->level - 1] &= ~layer->access;
 
 		/* Collect rule flags for each layer. */
-		if (rule_flags && layer->flags.quiet)
-			rule_flags->quiet_masks |= layer_bit;
+		if (rule_flags) {
+			if (layer->flags.quiet)
+				rule_flags->quiet_masks |= layer_bit;
+			if (layer->flags.no_inherit)
+				rule_flags->no_inherit_masks |= layer_bit;
+			if (layer->flags.has_no_inherit_descendant)
+				rule_flags->no_inherit_desc_masks |= layer_bit;
+		}
 	}
 
 	for (size_t i = 0; i < ARRAY_SIZE(masks->access); i++) {
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index e369f15ae885..34b70da8bd50 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -40,6 +40,20 @@ struct landlock_layer {
 		 * down the file hierarchy.
 		 */
 		bool quiet:1;
+		/**
+		 * @no_inherit: Prevents this rule from inheriting access rights
+		 * from ancestor inodes. Only used for filesystem rules.
+		 */
+		bool no_inherit : 1;
+		/**
+		 * @has_no_inherit_descendant: Marker to indicate that this layer
+		 * has at least one descendant directory with a rule having the
+		 * no_inherit flag.  Only used for filesystem rules.
+		 * This "flag" is not set by the user, but by Landlock on
+		 * parent directories of rules when the child rule has
+		 * a rule with the no_inherit flag to deny topology changes.
+		 */
+		bool has_no_inherit_descendant : 1;
 	} flags;
 	/**
 	 * @access: Bitfield of allowed actions on the kernel object.  They are
@@ -62,6 +76,18 @@ struct collected_rule_flags {
 	 * @quiet_masks: Layers for which the quiet flag is effective.
 	 */
 	layer_mask_t quiet_masks;
+	/**
+	 * @no_inherit_masks: Layers for which the no_inherit flag is effective.
+	 */
+	layer_mask_t no_inherit_masks;
+	/**
+	 * @no_inherit_desc_masks: Layers for which the
+	 * has_no_inherit_descendant tag is effective.
+	 * This is not a flag itself, but a marker set on ancestors
+	 * of rules with the no_inherit flag to deny topology changes
+	 * in the direct parent path.
+	 */
+	layer_mask_t no_inherit_desc_masks;
 };
 
 /**
-- 
2.53.0

[PATCH v7 07/10] landlock: Add documentation for LANDLOCK_ADD_RULE_NO_INHERIT

[Justin Suess]

Adds documentation of the flag to the userspace api, describing
the functionality of the flag and parent directory protections.

Signed-off-by: Justin Suess <utilityemal77@gmail.com>
---

Notes:
    v6..v7 changes:
    
      * Bump the documented ABI for LANDLOCK_ADD_RULE_NO_INHERIT to 10.
    
    v5..v6 changes:
    
      * None
    
    v1..v5 changes:
    
      * Initial addition

 Documentation/userspace-api/landlock.rst | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/Documentation/userspace-api/landlock.rst b/Documentation/userspace-api/landlock.rst
index fd8b78c31f2f..f49e30a1599a 100644
--- a/Documentation/userspace-api/landlock.rst
+++ b/Documentation/userspace-api/landlock.rst
@@ -716,6 +716,23 @@ Starting with the Landlock ABI version 9, it is possible to restrict
 connections to pathname UNIX domain sockets (:manpage:`unix(7)`) using
 the new ``LANDLOCK_ACCESS_FS_RESOLVE_UNIX`` right.
 
+Filesystem inheritance suppression (ABI < 10)
+---------------------------------------------
+
+Starting with the Landlock ABI version 10, it is possible to prevent a directory
+or file from inheriting it's parent's access grants by using the
+``LANDLOCK_ADD_RULE_NO_INHERIT`` flag passed to sys_landlock_add_rule().  This
+can be useful for policies where a parent directory needs broader access than its
+children.
+
+To mitigate sandbox-restart attacks, the inode itself, and ancestors of inodes
+tagged with ``LANDLOCK_ADD_RULE_NO_INHERIT`` cannot be removed, renamed,
+reparented, or linked into/from other directories.
+
+These parent directory protections propagate up to the root. Further inheritance
+for grants originating beneath a ``LANDLOCK_ADD_RULE_NO_INHERIT`` tagged inode
+are not affected unless also tagged with this flag.
+
 .. _kernel_support:
 
 Kernel support
-- 
2.53.0

[PATCH v7 08/10] samples/landlock: Add LANDLOCK_ADD_RULE_NO_INHERIT to landlock-sandboxer

[Justin Suess]

Adds support to landlock-sandboxer with environment variable
LL_FS_NO_INHERIT, which can be tagged on any filesystem object to
suppress access right inheritance.

Cc: Tingmao Wang <m@maowtm.org>
Signed-off-by: Justin Suess <utilityemal77@gmail.com>
---

Notes:
    v6..v7 changes:
    
      * Bump ABI
    
    v4..v6 changes:
    
      * None
    
    v3..v4 changes:
    
      * Modified LL_FS_R(O/W)_NO_INHERIT variables to a single variable
        to allow access rule combination.
    
    v2..v3 changes:
    
      * Minor formatting fixes

 samples/landlock/sandboxer.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
index daba6da2fb74..8dc3b4471b36 100644
--- a/samples/landlock/sandboxer.c
+++ b/samples/landlock/sandboxer.c
@@ -60,6 +60,7 @@ static inline int landlock_restrict_self(const int ruleset_fd,
 #define ENV_FS_RW_NAME "LL_FS_RW"
 #define ENV_FS_QUIET_NAME "LL_FS_QUIET"
 #define ENV_FS_QUIET_ACCESS_NAME "LL_FS_QUIET_ACCESS"
+#define ENV_FS_NO_INHERIT_NAME "LL_FS_NO_INHERIT"
 #define ENV_TCP_BIND_NAME "LL_TCP_BIND"
 #define ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT"
 #define ENV_NET_QUIET_NAME "LL_NET_QUIET"
@@ -385,6 +386,7 @@ static const char help[] =
 	"but to test audit we can set " ENV_FORCE_LOG_NAME "=1\n"
 	ENV_FS_QUIET_NAME " and " ENV_NET_QUIET_NAME ", both optional, can then be used "
 	"to make access to some denied paths or network ports not trigger audit logging.\n"
+	ENV_FS_NO_INHERIT_NAME " can be used to suppress access right propagation (ABI >= 10).\n"
 	ENV_FS_QUIET_ACCESS_NAME " and " ENV_NET_QUIET_ACCESS_NAME " can be used to specify "
 	"which accesses should be quieted (defaults to all):\n"
 	"* " ENV_FS_QUIET_ACCESS_NAME ": file system accesses to quiet\n"
@@ -432,6 +434,7 @@ int main(const int argc, char *const argv[], char *const *const envp)
 	};
 
 	bool quiet_supported = true;
+	bool no_inherit_supported = true;
 	int supported_restrict_flags = LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON;
 	int set_restrict_flags = 0;
 
@@ -526,6 +529,7 @@ int main(const int argc, char *const argv[], char *const *const envp)
 	case 9:
 		/* Don't add quiet flags for ABI < 10 later on. */
 		quiet_supported = false;
+		no_inherit_supported = false;
 
 		__attribute__((fallthrough));
 	case LANDLOCK_ABI_LAST:
@@ -612,6 +616,13 @@ int main(const int argc, char *const argv[], char *const *const envp)
 			goto err_close_ruleset;
 	}
 
+	/* Don't require this env to be present. */
+	if (no_inherit_supported && getenv(ENV_FS_NO_INHERIT_NAME)) {
+		if (populate_ruleset_fs(ENV_FS_NO_INHERIT_NAME, ruleset_fd, 0,
+					LANDLOCK_ADD_RULE_NO_INHERIT))
+			goto err_close_ruleset;
+	}
+
 	if (populate_ruleset_net(ENV_TCP_BIND_NAME, ruleset_fd,
 				 LANDLOCK_ACCESS_NET_BIND_TCP, 0)) {
 		goto err_close_ruleset;
-- 
2.53.0

[PATCH v7 09/10] selftests/landlock: Implement selftests for LANDLOCK_ADD_RULE_NO_INHERIT

[Justin Suess]

Implements 15 selftests for the flag, covering allowed and disallowed
operations on parent and child directories when this flag is set, as
well as multi-layer configurations and flag inheritance / audit
logging. Also tests a bind mount configuration.

Signed-off-by: Justin Suess <utilityemal77@gmail.com>
---

Notes:
    v6..v7 changes:
    
      * Reword misleading MAKE_REG comment.
    
    v5..v6 changes:
    
      * Remove redundant tree diagram from comment
    
    v4..v5 changes:
    
      * Fixed a bug in a test applying invalid access rights
        to a file.
    
    v3..v4 changes:
    
      * Added 4 new tests for bind mount handling, increasing selftests
        from 11 -> 15.
    
    v2..v3 changes:
    
      * Also covers flag inheritance, audit logging and
        LANDLOCK_ADD_RULE_QUIET suppression.
      * Increases number of selftests from 5 -> 11.

 tools/testing/selftests/landlock/fs_test.c | 705 +++++++++++++++++++++
 1 file changed, 705 insertions(+)

diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 2e32295258f9..28096576928d 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -1429,6 +1429,111 @@ TEST_F_FORK(layout1, inherit_superset)
 	ASSERT_EQ(0, test_open(file1_s1d3, O_RDONLY));
 }
 
+TEST_F_FORK(layout1, inherit_no_inherit_flag)
+{
+	struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_fs = ACCESS_RW,
+	};
+	int ruleset_fd;
+
+	ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+
+	add_path_beneath(_metadata, ruleset_fd, ACCESS_RW, dir_s1d1, 0);
+	add_path_beneath(_metadata, ruleset_fd, ACCESS_RO, dir_s1d2,
+			 LANDLOCK_ADD_RULE_NO_INHERIT);
+
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	/* Parent directory still grants write access to its direct children. */
+	EXPECT_EQ(0, test_open(dir_s1d1, O_RDONLY | O_DIRECTORY));
+	EXPECT_EQ(0, test_open(file1_s1d1, O_WRONLY));
+
+	/* dir_s1d2 gets only its explicit read-only access rights. */
+	EXPECT_EQ(0, test_open(dir_s1d2, O_RDONLY | O_DIRECTORY));
+	EXPECT_EQ(0, test_open(file1_s1d2, O_RDONLY));
+	EXPECT_EQ(EACCES, test_open(file1_s1d2, O_WRONLY));
+
+	/* Descendants of dir_s1d2 inherit the reduced access mask. */
+	EXPECT_EQ(0, test_open(dir_s1d3, O_RDONLY | O_DIRECTORY));
+	EXPECT_EQ(0, test_open(file1_s1d3, O_RDONLY));
+	EXPECT_EQ(EACCES, test_open(file1_s1d3, O_WRONLY));
+}
+
+TEST_F_FORK(layout1, inherit_no_inherit_nested_levels)
+{
+	int ruleset_fd;
+	struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_fs = ACCESS_RW | LANDLOCK_ACCESS_FS_REFER |
+				     LANDLOCK_ACCESS_FS_REMOVE_FILE |
+				     LANDLOCK_ACCESS_FS_REMOVE_DIR,
+	};
+
+	ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+
+	/* Level 1: s1d1 (RW + REFER + REMOVE + NO_INHERIT) */
+	add_path_beneath(_metadata, ruleset_fd,
+			 ACCESS_RW | LANDLOCK_ACCESS_FS_REFER |
+				 LANDLOCK_ACCESS_FS_REMOVE_FILE |
+				 LANDLOCK_ACCESS_FS_REMOVE_DIR,
+			 dir_s1d1, LANDLOCK_ADD_RULE_NO_INHERIT);
+
+	/* Level 2: s1d2 (RO + NO_INHERIT) */
+	add_path_beneath(_metadata, ruleset_fd, ACCESS_RO, dir_s1d2,
+			 LANDLOCK_ADD_RULE_NO_INHERIT);
+
+	/* Level 3: s1d3 (RW + REFER + REMOVE + NO_INHERIT) */
+	add_path_beneath(_metadata, ruleset_fd,
+			 ACCESS_RW | LANDLOCK_ACCESS_FS_REFER |
+				 LANDLOCK_ACCESS_FS_REMOVE_FILE |
+				 LANDLOCK_ACCESS_FS_REMOVE_DIR,
+			 dir_s1d3, LANDLOCK_ADD_RULE_NO_INHERIT);
+
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	/*
+	 * Level 3: s1d3
+	 * - RW allowed (unlink file)
+	 * - REFER allowed (rename file)
+	 * - REMOVE_DIR denied (parent s1d2 is part of direct parent tree)
+	 */
+	ASSERT_EQ(0, unlink(file1_s1d3));
+	ASSERT_EQ(0, rename(file2_s1d3, file1_s1d3));
+	ASSERT_EQ(0, rename(file1_s1d3, file2_s1d3));
+	ASSERT_EQ(-1, rmdir(dir_s1d3));
+	ASSERT_EQ(EACCES, errno);
+
+	/*
+	 * Level 2: s1d2
+	 * - RW denied (unlink file), layer is RO
+	 * - REFER denied (rename file)
+	 * - REMOVE_DIR of s1d2 not allowed (parent s1d1 is part of direct parent tree)
+	 */
+	ASSERT_EQ(-1, unlink(file1_s1d2));
+	ASSERT_EQ(EACCES, errno);
+	ASSERT_EQ(-1, rename(file2_s1d2, file1_s1d2));
+	ASSERT_EQ(EACCES, errno);
+	ASSERT_EQ(-1, rmdir(dir_s1d2));
+	ASSERT_EQ(EACCES, errno);
+
+	/*
+	 * Level 1: s1d1
+	 * - RW allowed
+	 * - Rename allowed (except for direct parent tree s1d2)
+	 * - REMOVE_DIR denied (parent tmp is denied)
+	 */
+	ASSERT_EQ(0, unlink(file1_s1d1));
+	ASSERT_EQ(0, rename(file2_s1d1, file1_s1d1));
+	ASSERT_EQ(0, rename(file1_s1d1, file2_s1d1));
+	ASSERT_EQ(-1, rmdir(dir_s1d1));
+	ASSERT_EQ(EACCES, errno);
+}
+
 TEST_F_FORK(layout0, max_layers)
 {
 	int i, err;
@@ -4179,6 +4284,266 @@ TEST_F_FORK(layout1, named_unix_domain_socket_ioctl)
 	EXPECT_EQ(0, close(srv_fd));
 }
 
+TEST_F_FORK(layout1, inherit_no_inherit_topology_dir)
+{
+	const struct rule rules[] = {
+		{
+			.path = TMP_DIR,
+			.access = ACCESS_RW | LANDLOCK_ACCESS_FS_REMOVE_FILE,
+		},
+		{},
+	};
+	int ruleset_fd;
+
+	ruleset_fd = create_ruleset(_metadata,
+				    ACCESS_RW | LANDLOCK_ACCESS_FS_REMOVE_FILE,
+				    rules);
+	ASSERT_LE(0, ruleset_fd);
+
+	/* Adds a no-inherit rule on a leaf directory. */
+	add_path_beneath(_metadata, ruleset_fd, ACCESS_RO, dir_s1d3,
+			 LANDLOCK_ADD_RULE_NO_INHERIT);
+
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	/*
+	 * Topology modifications of the rule path and its parents are denied.
+	 */
+
+	/* Target directory s1d3 */
+	ASSERT_EQ(-1, rmdir(dir_s1d3));
+	ASSERT_EQ(EACCES, errno);
+	ASSERT_EQ(-1, rename(dir_s1d3, dir_s2d3));
+	ASSERT_EQ(EACCES, errno);
+
+	/* Parent directory s1d2 */
+	ASSERT_EQ(-1, rmdir(dir_s1d2));
+	ASSERT_EQ(EACCES, errno);
+	ASSERT_EQ(-1, rename(dir_s1d2, dir_s2d2));
+	ASSERT_EQ(EACCES, errno);
+
+	/* Grandparent directory s1d1 */
+	ASSERT_EQ(-1, rmdir(dir_s1d1));
+	ASSERT_EQ(EACCES, errno);
+	ASSERT_EQ(-1, rename(dir_s1d1, dir_s2d1));
+	ASSERT_EQ(EACCES, errno);
+
+	/*
+	 * Sibling operations are allowed.
+	 */
+	/* Sibling of s1d3 */
+	ASSERT_EQ(0, unlink(file1_s1d2));
+	/* Sibling of s1d2 */
+	ASSERT_EQ(0, unlink(file1_s1d1));
+
+	/*
+	 * Content of the no-inherit directory is restricted by the rule (RO).
+	 */
+	ASSERT_EQ(-1, unlink(file1_s1d3));
+	ASSERT_EQ(EACCES, errno);
+}
+
+TEST_F_FORK(layout1, no_inherit_allow_inner_removal)
+{
+	int ruleset_fd;
+	struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_fs = ACCESS_RW | LANDLOCK_ACCESS_FS_REMOVE_FILE,
+	};
+
+	ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+
+	add_path_beneath(_metadata, ruleset_fd,
+			 ACCESS_RW | LANDLOCK_ACCESS_FS_REMOVE_FILE, dir_s1d2,
+			 LANDLOCK_ADD_RULE_NO_INHERIT);
+
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	/*
+	 * Content of the no-inherit directory is mutable (RW).
+	 * This checks that the no-inherit flag does not seal the content.
+	 */
+	ASSERT_EQ(0, unlink(file1_s1d2));
+
+	/*
+	 * Topology modifications of the rule path are denied.
+	 */
+	ASSERT_EQ(-1, rmdir(dir_s1d2));
+	ASSERT_EQ(EACCES, errno);
+	ASSERT_EQ(-1, rename(dir_s1d2, dir_s2d2));
+	ASSERT_EQ(EACCES, errno);
+}
+
+TEST_F_FORK(layout1, inherit_no_inherit_topology_unrelated)
+{
+	const struct rule rules[] = {
+		{
+			.path = TMP_DIR,
+			.access = ACCESS_RW,
+		},
+		{},
+	};
+	static const char unrelated_dir[] = TMP_DIR "/s2d1/unrelated";
+	static const char unrelated_file[] = TMP_DIR "/s2d1/unrelated/f1";
+	int ruleset_fd;
+
+	ruleset_fd = create_ruleset(_metadata, ACCESS_RW, rules);
+	ASSERT_LE(0, ruleset_fd);
+
+	/* Adds a no-inherit rule on a leaf directory unrelated to s2. */
+	add_path_beneath(_metadata, ruleset_fd, ACCESS_RO, dir_s1d3,
+			 LANDLOCK_ADD_RULE_NO_INHERIT);
+
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	/* Ensure we can still create and delete files outside the sealed branch. */
+	ASSERT_EQ(0, mkdir(unrelated_dir, 0700));
+	ASSERT_EQ(0, mknod(unrelated_file, S_IFREG | 0600, 0));
+	ASSERT_EQ(0, unlink(unrelated_file));
+	ASSERT_EQ(0, rmdir(unrelated_dir));
+
+	/* Existing siblings in s2 remain modifiable. */
+	ASSERT_EQ(0, unlink(file1_s2d1));
+	ASSERT_EQ(0, mknod(file1_s2d1, S_IFREG | 0700, 0));
+}
+
+TEST_F_FORK(layout1, inherit_no_inherit_descendant_rw)
+{
+	const struct rule rules[] = {
+		{
+			.path = TMP_DIR,
+			.access = ACCESS_RO,
+		},
+		{},
+	};
+	const __u64 handled_access = ACCESS_RW | LANDLOCK_ACCESS_FS_MAKE_REG |
+				     LANDLOCK_ACCESS_FS_REMOVE_FILE;
+	static const char child_file[] =
+		TMP_DIR "/s1d1/s1d2/s1d3/rw_descendant";
+	int ruleset_fd;
+
+	ruleset_fd = create_ruleset(_metadata, handled_access, rules);
+	ASSERT_LE(0, ruleset_fd);
+
+	add_path_beneath(_metadata, ruleset_fd, ACCESS_RO, dir_s1d2,
+			 LANDLOCK_ADD_RULE_NO_INHERIT);
+	add_path_beneath(_metadata, ruleset_fd,
+			 ACCESS_RW | LANDLOCK_ACCESS_FS_MAKE_REG |
+				 LANDLOCK_ACCESS_FS_REMOVE_FILE,
+			 dir_s1d3, 0);
+
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	ASSERT_EQ(0, mknod(child_file, S_IFREG | 0600, 0));
+	ASSERT_EQ(0, unlink(child_file));
+}
+
+TEST_F_FORK(layout1, inherit_no_inherit_topology_file)
+{
+	const struct rule rules[] = {
+		{
+			.path = TMP_DIR,
+			.access = ACCESS_RW,
+		},
+		{},
+	};
+	int ruleset_fd;
+
+	/*
+	 * Both file1_s1d2 and file2_s1d2 already exist from the fixture.
+	 * file2_s1d2 is in the same directory as file1_s1d2 and will be
+	 * used to test inheritance vs. NO_INHERIT behavior.
+	 */
+
+	ruleset_fd = create_ruleset(_metadata, ACCESS_RW, rules);
+	ASSERT_LE(0, ruleset_fd);
+
+	/*
+	 * Add a NO_INHERIT rule on file1_s1d2 with READ_FILE access.
+	 * This should succeed (files can have NO_INHERIT).
+	 * Use READ_FILE (not ACCESS_RO which includes READ_DIR) since
+	 * directory access rights don't make sense for files.
+	 */
+	add_path_beneath(_metadata, ruleset_fd, LANDLOCK_ACCESS_FS_READ_FILE,
+			 file1_s1d2, LANDLOCK_ADD_RULE_NO_INHERIT);
+
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	/*
+	 * file1_s1d2 has NO_INHERIT with READ_FILE access only,
+	 * so it should only be readable (not inheriting RW from parent TMP_DIR).
+	 */
+	ASSERT_EQ(0, test_open(file1_s1d2, O_RDONLY));
+	ASSERT_EQ(EACCES, test_open(file1_s1d2, O_WRONLY));
+
+	/*
+	 * file2_s1d2 does not have NO_INHERIT, so it should inherit
+	 * RW access from parent TMP_DIR rule.
+	 */
+	ASSERT_EQ(0, test_open(file2_s1d2, O_RDONLY));
+	ASSERT_EQ(0, test_open(file2_s1d2, O_WRONLY));
+}
+
+TEST_F_FORK(layout1, inherit_no_inherit_layered)
+{
+	const struct rule layer1_and_2[] = {
+		{
+			.path = TMP_DIR,
+			.access = ACCESS_RW | LANDLOCK_ACCESS_FS_REMOVE_FILE,
+		},
+		{},
+	};
+	int ruleset_fd;
+	static const char unrelated_dir[] = TMP_DIR "/s2d1/unrelated";
+	static const char unrelated_file[] = TMP_DIR "/s2d1/unrelated/f1";
+
+	/* Layer 1: RW on TMP_DIR */
+	ruleset_fd = create_ruleset(_metadata,
+				    ACCESS_RW | LANDLOCK_ACCESS_FS_REMOVE_FILE,
+				    layer1_and_2);
+	ASSERT_LE(0, ruleset_fd);
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	/* Layer 2: Add no-inherit RO rule on s1d2 */
+	ruleset_fd = create_ruleset(_metadata,
+				    ACCESS_RW | LANDLOCK_ACCESS_FS_REMOVE_FILE,
+				    layer1_and_2);
+	ASSERT_LE(0, ruleset_fd);
+	add_path_beneath(_metadata, ruleset_fd, ACCESS_RO, dir_s1d2,
+			 LANDLOCK_ADD_RULE_NO_INHERIT);
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	/* Operations in unrelated areas should still work */
+	ASSERT_EQ(0, mkdir(unrelated_dir, 0700));
+	ASSERT_EQ(0, mknod(unrelated_file, S_IFREG | 0600, 0));
+	ASSERT_EQ(0, unlink(unrelated_file));
+	ASSERT_EQ(0, rmdir(unrelated_dir));
+
+	/* Creating in s1d1 should be allowed (parent still has RW) */
+	ASSERT_EQ(0, mknod(TMP_DIR "/s1d1/newfile", S_IFREG | 0600, 0));
+	ASSERT_EQ(0, unlink(TMP_DIR "/s1d1/newfile"));
+
+	/* Content of s1d2 should be read-only */
+	ASSERT_EQ(-1, unlink(file1_s1d2));
+	ASSERT_EQ(EACCES, errno);
+
+	/* Topology changes to s1d2 should be denied */
+	ASSERT_EQ(-1, rename(dir_s1d2, TMP_DIR "/s2d1/renamed"));
+	ASSERT_EQ(EACCES, errno);
+
+	/* Renaming s1d1 should also be denied (it's an ancestor) */
+	ASSERT_EQ(-1, rename(dir_s1d1, TMP_DIR "/s2d1/renamed"));
+	ASSERT_EQ(EACCES, errno);
+}
+
 /* clang-format off */
 FIXTURE(ioctl) {};
 
@@ -5931,6 +6296,252 @@ TEST_F_FORK(layout4_disconnected_leafs, read_rename_exchange)
 		  test_renameat(s1d42_bind_fd, "f4", s1d42_bind_fd, "f5"));
 }
 
+/*
+ * When s1d41 (accessed via the mount at s2d2) is protected with NO_INHERIT,
+ * its parent directories within the mount (s1d31) should be immovable.
+ */
+TEST_F_FORK(layout4_disconnected_leafs, no_inherit_mount_parent_rename)
+{
+	int ruleset_fd, s1d41_bind_fd;
+	struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_fs = ACCESS_RW | LANDLOCK_ACCESS_FS_REFER |
+				     LANDLOCK_ACCESS_FS_REMOVE_FILE |
+				     LANDLOCK_ACCESS_FS_REMOVE_DIR,
+	};
+
+	ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+
+	/* Allow full access to TMP_DIR. */
+	add_path_beneath(_metadata, ruleset_fd,
+			 ACCESS_RW | LANDLOCK_ACCESS_FS_REFER |
+				 LANDLOCK_ACCESS_FS_REMOVE_FILE |
+				 LANDLOCK_ACCESS_FS_REMOVE_DIR,
+			 TMP_DIR, 0);
+
+	/*
+	 * Access s1d41 through the bind mount at s2d2 and protect it with
+	 * NO_INHERIT. This should seal the parent hierarchy through the mount.
+	 */
+	s1d41_bind_fd = open(TMP_DIR "/s2d1/s2d2/s1d31/s1d41",
+			     O_DIRECTORY | O_PATH | O_CLOEXEC);
+	ASSERT_LE(0, s1d41_bind_fd);
+
+	ASSERT_EQ(0, landlock_add_rule(ruleset_fd, LANDLOCK_RULE_PATH_BENEATH,
+				       &(struct landlock_path_beneath_attr){
+					       .parent_fd = s1d41_bind_fd,
+					       .allowed_access = ACCESS_RO,
+				       },
+				       LANDLOCK_ADD_RULE_NO_INHERIT));
+	EXPECT_EQ(0, close(s1d41_bind_fd));
+
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	/*
+	 * s1d31 is the parent of s1d41 within the mount. Renaming it should
+	 * be denied because it is part of the protected parent hierarchy.
+	 * Test via the mount path.
+	 */
+	ASSERT_EQ(-1, rename(TMP_DIR "/s2d1/s2d2/s1d31",
+			     TMP_DIR "/s2d1/s2d2/s1d31_renamed"));
+	ASSERT_EQ(EACCES, errno);
+
+	/*
+	 * s1d32 is a sibling directory (not in the protected parent chain),
+	 * so renaming it should be allowed.
+	 */
+	ASSERT_EQ(0, rename(TMP_DIR "/s2d1/s2d2/s1d32",
+			    TMP_DIR "/s2d1/s2d2/s1d32_renamed"));
+	ASSERT_EQ(0, rename(TMP_DIR "/s2d1/s2d2/s1d32_renamed",
+			    TMP_DIR "/s2d1/s2d2/s1d32"));
+
+	/*
+	 * Renaming directories not in the protected parent hierarchy should
+	 * still be allowed.
+	 */
+	ASSERT_EQ(0, rename(TMP_DIR "/s3d1", TMP_DIR "/s3d1_renamed"));
+	ASSERT_EQ(0, rename(TMP_DIR "/s3d1_renamed", TMP_DIR "/s3d1"));
+}
+
+TEST_F_FORK(layout4_disconnected_leafs, no_inherit_mount_parent_rmdir)
+{
+	int ruleset_fd, s1d41_bind_fd;
+	struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_fs = ACCESS_RW | LANDLOCK_ACCESS_FS_REFER |
+				     LANDLOCK_ACCESS_FS_REMOVE_FILE |
+				     LANDLOCK_ACCESS_FS_REMOVE_DIR,
+	};
+
+	ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+
+	/* Allow full access to TMP_DIR. */
+	add_path_beneath(_metadata, ruleset_fd,
+			 ACCESS_RW | LANDLOCK_ACCESS_FS_REFER |
+				 LANDLOCK_ACCESS_FS_REMOVE_FILE |
+				 LANDLOCK_ACCESS_FS_REMOVE_DIR,
+			 TMP_DIR, 0);
+
+	/*
+	 * Access s1d41 through the bind mount at s2d2 and protect it with
+	 * NO_INHERIT. This should seal the parent hierarchy through the mount.
+	 */
+	s1d41_bind_fd = open(TMP_DIR "/s2d1/s2d2/s1d31/s1d41",
+			     O_DIRECTORY | O_PATH | O_CLOEXEC);
+	ASSERT_LE(0, s1d41_bind_fd);
+
+	ASSERT_EQ(0, landlock_add_rule(ruleset_fd, LANDLOCK_RULE_PATH_BENEATH,
+				       &(struct landlock_path_beneath_attr){
+					       .parent_fd = s1d41_bind_fd,
+					       .allowed_access = ACCESS_RO,
+				       },
+				       LANDLOCK_ADD_RULE_NO_INHERIT));
+	EXPECT_EQ(0, close(s1d41_bind_fd));
+
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	/*
+	 * s1d31 is the parent of s1d41 within the mount. Removing it should
+	 * be denied because it is part of the protected parent hierarchy.
+	 */
+	ASSERT_EQ(-1, rmdir(TMP_DIR "/s2d1/s2d2/s1d31"));
+	ASSERT_EQ(EACCES, errno);
+
+	/*
+	 * Removing an unrelated directory should still be allowed (if empty).
+	 */
+	ASSERT_EQ(0, rmdir(TMP_DIR "/s3d1"));
+	ASSERT_EQ(0, mkdir(TMP_DIR "/s3d1", 0755));
+}
+
+TEST_F_FORK(layout4_disconnected_leafs, no_inherit_mount_parent_link)
+{
+	int ruleset_fd, s1d41_bind_fd;
+	struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_fs = ACCESS_RW | LANDLOCK_ACCESS_FS_REFER |
+				     LANDLOCK_ACCESS_FS_REMOVE_FILE |
+				     LANDLOCK_ACCESS_FS_REMOVE_DIR |
+				     LANDLOCK_ACCESS_FS_MAKE_REG,
+	};
+
+	ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+
+	/* Allow full access to TMP_DIR. */
+	add_path_beneath(_metadata, ruleset_fd,
+			 ACCESS_RW | LANDLOCK_ACCESS_FS_REFER |
+				 LANDLOCK_ACCESS_FS_REMOVE_FILE |
+				 LANDLOCK_ACCESS_FS_REMOVE_DIR |
+				 LANDLOCK_ACCESS_FS_MAKE_REG,
+			 TMP_DIR, 0);
+
+	/*
+	 * Access s1d41 through the bind mount at s2d2 and protect it with
+	 * NO_INHERIT. This should seal the parent hierarchy through the mount.
+	 */
+	s1d41_bind_fd = open(TMP_DIR "/s2d1/s2d2/s1d31/s1d41",
+			     O_DIRECTORY | O_PATH | O_CLOEXEC);
+	ASSERT_LE(0, s1d41_bind_fd);
+
+	ASSERT_EQ(0, landlock_add_rule(ruleset_fd, LANDLOCK_RULE_PATH_BENEATH,
+				       &(struct landlock_path_beneath_attr){
+					       .parent_fd = s1d41_bind_fd,
+					       .allowed_access = ACCESS_RO,
+				       },
+				       LANDLOCK_ADD_RULE_NO_INHERIT));
+	EXPECT_EQ(0, close(s1d41_bind_fd));
+
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	/*
+	 * Creating a hard link within the protected NO_INHERIT directory should
+	 * be denied because NO_INHERIT grants only ACCESS_RO (MAKE_REG is not
+	 * inherited). Test via the mount path.
+	 */
+	ASSERT_EQ(-1, linkat(AT_FDCWD, TMP_DIR "/s2d1/s2d2/s1d31/s1d41/f1",
+			     AT_FDCWD, TMP_DIR "/s2d1/s2d2/s1d31/s1d41/f1_link",
+			     0));
+	ASSERT_EQ(EACCES, errno);
+
+	/*
+	 * Creating links within directories outside the protected chain
+	 * (using the mount source path to avoid EXDEV) should still be allowed.
+	 */
+	ASSERT_EQ(0, linkat(AT_FDCWD, TMP_DIR "/s1d1/s1d2/s1d32/s1d42/f3",
+			    AT_FDCWD, TMP_DIR "/s1d1/s1d2/s1d32/s1d42/f3_link",
+			    0));
+	ASSERT_EQ(0, unlink(TMP_DIR "/s1d1/s1d2/s1d32/s1d42/f3_link"));
+}
+
+/*
+ * Test that NO_INHERIT protection extends to the mount source hierarchy.
+ * If a directory is protected via a mount path, its parents within the
+ * mount source should also be protected from topology changes.
+ */
+TEST_F_FORK(layout4_disconnected_leafs, no_inherit_source_parent_rename)
+{
+	int ruleset_fd, s1d41_bind_fd;
+	struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_fs = ACCESS_RW | LANDLOCK_ACCESS_FS_REFER |
+				     LANDLOCK_ACCESS_FS_REMOVE_FILE |
+				     LANDLOCK_ACCESS_FS_REMOVE_DIR,
+	};
+
+	ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+
+	/* Allow full access to TMP_DIR. */
+	add_path_beneath(_metadata, ruleset_fd,
+			 ACCESS_RW | LANDLOCK_ACCESS_FS_REFER |
+				 LANDLOCK_ACCESS_FS_REMOVE_FILE |
+				 LANDLOCK_ACCESS_FS_REMOVE_DIR,
+			 TMP_DIR, 0);
+
+	/*
+	 * Access s1d41 through the bind mount at s2d2 and protect it with
+	 * NO_INHERIT. The source mount path parents should also be protected.
+	 */
+	s1d41_bind_fd = open(TMP_DIR "/s2d1/s2d2/s1d31/s1d41",
+			     O_DIRECTORY | O_PATH | O_CLOEXEC);
+	ASSERT_LE(0, s1d41_bind_fd);
+
+	ASSERT_EQ(0, landlock_add_rule(ruleset_fd, LANDLOCK_RULE_PATH_BENEATH,
+				       &(struct landlock_path_beneath_attr){
+					       .parent_fd = s1d41_bind_fd,
+					       .allowed_access = ACCESS_RO,
+				       },
+				       LANDLOCK_ADD_RULE_NO_INHERIT));
+	EXPECT_EQ(0, close(s1d41_bind_fd));
+
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	/*
+	 * The mount source is s1d1/s1d2. The protected directory s1d41 is at
+	 * s1d1/s1d2/s1d31/s1d41. The parent s1d31 within the mount source
+	 * should be protected from topology changes.
+	 */
+	ASSERT_EQ(-1, rename(TMP_DIR "/s1d1/s1d2/s1d31",
+			     TMP_DIR "/s1d1/s1d2/s1d31_renamed"));
+	ASSERT_EQ(EACCES, errno);
+
+	/*
+	 * s1d32 is a sibling, not in the protected parent chain. It should
+	 * be renamable.
+	 */
+	ASSERT_EQ(0, rename(TMP_DIR "/s1d1/s1d2/s1d32",
+			    TMP_DIR "/s1d1/s1d2/s1d32_renamed"));
+	ASSERT_EQ(0, rename(TMP_DIR "/s1d1/s1d2/s1d32_renamed",
+			    TMP_DIR "/s1d1/s1d2/s1d32"));
+}
+
 /*
  * layout5_disconnected_branch before rename:
  *
@@ -7358,6 +7969,100 @@ TEST_F(audit_layout1, write_file)
 	EXPECT_EQ(1, records.domain);
 }
 
+TEST_F(audit_layout1, no_inherit_parent_is_logged)
+{
+	struct audit_records records;
+	struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_fs = ACCESS_RW,
+	};
+	int ruleset_fd;
+
+	ruleset_fd = landlock_create_ruleset(&ruleset_attr,
+					     sizeof(ruleset_attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+
+	/* Base read-only rule at s1d1. */
+	add_path_beneath(_metadata, ruleset_fd, ACCESS_RO, dir_s1d1, 0);
+	/* Descendant s1d1/s1d2/s1d3 forbids inheritance but should still log. */
+	add_path_beneath(_metadata, ruleset_fd, ACCESS_RO, dir_s1d3,
+			 LANDLOCK_ADD_RULE_NO_INHERIT);
+
+	enforce_ruleset(_metadata, ruleset_fd);
+
+	EXPECT_EQ(EACCES, test_open(file1_s1d2, O_WRONLY));
+	EXPECT_EQ(0, matches_log_fs(_metadata, self->audit_fd,
+				    "fs\\.write_file", file1_s1d2));
+	EXPECT_EQ(0, audit_count_records(self->audit_fd, &records));
+	EXPECT_EQ(0, records.access);
+	EXPECT_EQ(1, records.domain);
+
+	EXPECT_EQ(0, close(ruleset_fd));
+}
+
+TEST_F(audit_layout1, no_inherit_blocks_quiet_flag_inheritance)
+{
+	struct audit_records records;
+	struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_fs = ACCESS_RW,
+		.quiet_access_fs = ACCESS_RW,
+	};
+	int ruleset_fd;
+
+	ruleset_fd = landlock_create_ruleset(&ruleset_attr,
+					     sizeof(ruleset_attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+
+	/* Base read-only rule at tmp/s1d1 with quiet flag. */
+	add_path_beneath(_metadata, ruleset_fd, ACCESS_RO, dir_s1d1,
+			 LANDLOCK_ADD_RULE_QUIET);
+	/* Descendant tmp/s1d1/s1d2/s1d3 forbids inheritance of quiet flag and should still log. */
+	add_path_beneath(_metadata, ruleset_fd, ACCESS_RO, dir_s1d3,
+			 LANDLOCK_ADD_RULE_NO_INHERIT);
+
+	enforce_ruleset(_metadata, ruleset_fd);
+
+	EXPECT_EQ(EACCES, test_open(file1_s1d3, O_WRONLY));
+	EXPECT_EQ(0, matches_log_fs(_metadata, self->audit_fd,
+				    "fs\\.write_file", file1_s1d3));
+	EXPECT_EQ(0, audit_count_records(self->audit_fd, &records));
+	EXPECT_EQ(0, records.access);
+	EXPECT_EQ(1, records.domain);
+
+	EXPECT_EQ(0, close(ruleset_fd));
+}
+
+TEST_F(audit_layout1, no_inherit_quiet_parent)
+{
+	struct audit_records records;
+	struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_fs = ACCESS_RW,
+		.quiet_access_fs = ACCESS_RW,
+	};
+	int ruleset_fd;
+
+	ruleset_fd = landlock_create_ruleset(&ruleset_attr,
+					     sizeof(ruleset_attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+
+	/* Base read-only rule at tmp/s1d1 with quiet flag. */
+	add_path_beneath(_metadata, ruleset_fd, ACCESS_RO, dir_s1d1,
+			 LANDLOCK_ADD_RULE_QUIET);
+	/* Access to dir_s1d1 shouldn't log */
+	add_path_beneath(_metadata, ruleset_fd, ACCESS_RO, dir_s1d3,
+			 LANDLOCK_ADD_RULE_NO_INHERIT);
+
+	enforce_ruleset(_metadata, ruleset_fd);
+
+	EXPECT_EQ(EACCES, test_open(file1_s1d1, O_WRONLY));
+	EXPECT_NE(0, matches_log_fs(_metadata, self->audit_fd,
+				    "fs\\.write_file", file1_s1d1));
+	EXPECT_EQ(0, audit_count_records(self->audit_fd, &records));
+	EXPECT_EQ(0, records.access);
+	EXPECT_EQ(0, records.domain);
+
+	EXPECT_EQ(0, close(ruleset_fd));
+}
+
 TEST_F(audit_layout1, read_file)
 {
 	struct audit_records records;
-- 
2.53.0

[PATCH v7 10/10] landlock: Implement KUnit test for LANDLOCK_ADD_RULE_NO_INHERIT

[Justin Suess]

Add a unit test for rule_flag collection, ensuring that access masks
are properly propagated with the flags.

Signed-off-by: Justin Suess <utilityemal77@gmail.com>
---

Notes:
    v6..v7 changes:
    
      * None
    
    v4..v6 changes:
    
      * None
    
    v2..v3 changes:
    
      * Removed erroneously misplaced code and placed it in the proper
        patch.

 security/landlock/ruleset.c | 85 +++++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)

diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index 8fdba3a7f983..7bc5000e7485 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -22,6 +22,7 @@
 #include <linux/spinlock.h>
 #include <linux/workqueue.h>
 #include <uapi/linux/landlock.h>
+#include <kunit/test.h>
 
 #include "access.h"
 #include "domain.h"
@@ -753,3 +754,87 @@ landlock_init_layer_masks(const struct landlock_ruleset *const domain,
 
 	return handled_accesses;
 }
+
+#ifdef CONFIG_SECURITY_LANDLOCK_KUNIT_TEST
+
+/**
+ * test_unmask_layers_no_inherit - Test landlock_unmask_layers() with no_inherit
+ * @test: The KUnit test context.
+ */
+static void test_unmask_layers_no_inherit(struct kunit *const test)
+{
+	struct landlock_rule *rule;
+	struct layer_access_masks layer_masks = {};
+	struct collected_rule_flags rule_flags;
+	const access_mask_t access_request = BIT_ULL(0) | BIT_ULL(1);
+	size_t i;
+
+	rule = kzalloc(struct_size(rule, layers, 2), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, rule);
+
+	rule->num_layers = 2;
+
+	/* Layer 1: allows access 0, no_inherit */
+	rule->layers[0].level = 1;
+	rule->layers[0].access = BIT_ULL(0);
+	rule->layers[0].flags.no_inherit = 1;
+
+	/* Layer 2: allows access 1 */
+	rule->layers[1].level = 2;
+	rule->layers[1].access = BIT_ULL(1);
+
+	/* Case 1: No rule_flags provided (should behave normally) */
+	for (i = 0; i < ARRAY_SIZE(layer_masks.access); i++)
+		layer_masks.access[i] = access_request;
+
+	landlock_unmask_layers(rule, &layer_masks, NULL);
+
+	/* Access 0 should be unmasked by layer 1 */
+	KUNIT_EXPECT_EQ(test, layer_masks.access[0], access_request & ~BIT_ULL(0));
+	/* Access 1 should be unmasked by layer 2 */
+	KUNIT_EXPECT_EQ(test, layer_masks.access[1], access_request & ~BIT_ULL(1));
+
+	/* Case 2: rule_flags provided, no existing no_inherit_masks */
+	for (i = 0; i < ARRAY_SIZE(layer_masks.access); i++)
+		layer_masks.access[i] = access_request;
+	memset(&rule_flags, 0, sizeof(rule_flags));
+
+	landlock_unmask_layers(rule, &layer_masks, &rule_flags);
+
+	/* Access 0 should be unmasked by layer 1 */
+	KUNIT_EXPECT_EQ(test, layer_masks.access[0], access_request & ~BIT_ULL(0));
+	/* Access 1 should be unmasked by layer 2 */
+	KUNIT_EXPECT_EQ(test, layer_masks.access[1], access_request & ~BIT_ULL(1));
+
+	/* rule_flags should collect no_inherit from layer 1 */
+	KUNIT_EXPECT_EQ(test, rule_flags.no_inherit_masks, (layer_mask_t)BIT_ULL(0));
+
+	/* Case 3: rule_flags provided, layer 1 is masked by no_inherit_masks */
+	for (i = 0; i < ARRAY_SIZE(layer_masks.access); i++)
+		layer_masks.access[i] = access_request;
+	memset(&rule_flags, 0, sizeof(rule_flags));
+	rule_flags.no_inherit_masks = BIT_ULL(0); /* Mask layer 1 */
+
+	landlock_unmask_layers(rule, &layer_masks, &rule_flags);
+
+	/* Access 0 should NOT be unmasked by layer 1 because it is skipped */
+	KUNIT_EXPECT_EQ(test, layer_masks.access[0], access_request);
+	/* Access 1 should be unmasked by layer 2 */
+	KUNIT_EXPECT_EQ(test, layer_masks.access[1], access_request & ~BIT_ULL(1));
+
+	kfree(rule);
+}
+
+static struct kunit_case ruleset_test_cases[] = {
+	KUNIT_CASE(test_unmask_layers_no_inherit),
+	{}
+};
+
+static struct kunit_suite ruleset_test_suite = {
+	.name = "landlock_ruleset",
+	.test_cases = ruleset_test_cases,
+};
+
+kunit_test_suite(ruleset_test_suite);
+
+#endif /* CONFIG_SECURITY_LANDLOCK_KUNIT_TEST */
-- 
2.53.0