landlock: Add missing kernel-doc "Return:" sections

The kernel-doc -Wreturn check warns about functions with documentation
comments that lack a "Return:" section.  Add "Return:" documentation to
all functions missing it so that kernel-doc -Wreturn passes cleanly.

Convert existing function descriptions into a formal "Return:" section.
Also fix the inaccurate return documentation for
landlock_merge_ruleset() which claimed to return @parent directly, and
document the previously missing ERR_PTR() error return path.  Document
the ABI version and errata return paths for landlock_create_ruleset()
which were previously only implied by the prose.

Cc: Günther Noack <gnoack@google.com>
Reviewed-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20260304193134.250495-2-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>

security/landlock/domain.c

@@ -114,6 +114,8 @@ static struct landlock_details *get_current_details(void)
  * restriction.  The subjective credentials must not be in an overridden state.
  *
  * @hierarchy->parent and @hierarchy->usage should already be set.
+ *
+ * Return: 0 on success, -errno on failure.
  */
 int landlock_init_hierarchy_log(struct landlock_hierarchy *const hierarchy)
 {

security/landlock/fs.c

@@ -1568,7 +1568,7 @@ static int hook_path_truncate(const struct path *const path)
  *
  * @file: File being opened.
  *
- * Returns the access rights that are required for opening the given file,
+ * Return: The access rights that are required for opening the given file,
  * depending on the file type and open mode.
  */
 static access_mask_t

security/landlock/ruleset.c

@@ -201,6 +201,8 @@ static void build_check_ruleset(void)
  * When merging a ruleset in a domain, or copying a domain, @layers will be
  * added to @ruleset as new constraints, similarly to a boolean AND between
  * access rights.
+ *
+ * Return: 0 on success, -errno on failure.
  */
 static int insert_rule(struct landlock_ruleset *const ruleset,
 		       const struct landlock_id id,
@@ -530,8 +532,8 @@ void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset)
  * The current task is requesting to be restricted.  The subjective credentials
  * must not be in an overridden state. cf. landlock_init_hierarchy_log().
  *
- * Returns the intersection of @parent and @ruleset, or returns @parent if
- * @ruleset is empty, or returns a duplicate of @ruleset if @parent is empty.
+ * Return: A new domain merging @parent and @ruleset on success, or ERR_PTR()
+ * on failure.  If @parent is NULL, the new domain duplicates @ruleset.
  */
 struct landlock_ruleset *
 landlock_merge_ruleset(struct landlock_ruleset *const parent,
@@ -622,7 +624,7 @@ landlock_find_rule(const struct landlock_ruleset *const ruleset,
  * @rule: A rule that grants a set of access rights for each layer
  * @masks: A matrix of unfulfilled access rights for each layer
  *
- * Returns true if the request is allowed (i.e. the access rights granted all
+ * Return: True if the request is allowed (i.e. the access rights granted all
  * remaining unfulfilled access rights and masks has no leftover set bits).
  */
 bool landlock_unmask_layers(const struct landlock_rule *const rule,

security/landlock/syscalls.c

@@ -60,6 +60,8 @@ static bool is_initialized(void)
  * @ksize_min: Minimal required size to be copied.
  * @src: User space pointer or NULL.
  * @usize: (Alleged) size of the data pointed to by @src.
+ *
+ * Return: 0 on success, -errno on failure.
  */
 static __always_inline int
 copy_min_struct_from_user(void *const dst, const size_t ksize,
@@ -178,16 +180,19 @@ const int landlock_abi_version = 8;
  *         - %LANDLOCK_CREATE_RULESET_VERSION
  *         - %LANDLOCK_CREATE_RULESET_ERRATA
  *
- * This system call enables to create a new Landlock ruleset, and returns the
- * related file descriptor on success.
+ * This system call enables to create a new Landlock ruleset.
  *
  * If %LANDLOCK_CREATE_RULESET_VERSION or %LANDLOCK_CREATE_RULESET_ERRATA is
  * set, then @attr must be NULL and @size must be 0.
  *
- * Possible returned errors are:
+ * Return: The ruleset file descriptor on success, the Landlock ABI version if
+ * %LANDLOCK_CREATE_RULESET_VERSION is set, the errata value if
+ * %LANDLOCK_CREATE_RULESET_ERRATA is set, or -errno on failure.  Possible
+ * returned errors are:
  *
  * - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time;
- * - %EINVAL: unknown @flags, or unknown access, or unknown scope, or too small @size;
+ * - %EINVAL: unknown @flags, or unknown access, or unknown scope, or too small
+ *   @size;
  * - %E2BIG: @attr or @size inconsistencies;
  * - %EFAULT: @attr or @size inconsistencies;
  * - %ENOMSG: empty &landlock_ruleset_attr.handled_access_fs.
@@ -398,7 +403,7 @@ static int add_rule_net_port(struct landlock_ruleset *ruleset,
  * This system call enables to define a new rule and add it to an existing
  * ruleset.
  *
- * Possible returned errors are:
+ * Return: 0 on success, or -errno on failure.  Possible returned errors are:
  *
  * - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time;
  * - %EAFNOSUPPORT: @rule_type is %LANDLOCK_RULE_NET_PORT but TCP/IP is not
@@ -464,7 +469,7 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
  * namespace or is running with no_new_privs.  This avoids scenarios where
  * unprivileged tasks can affect the behavior of privileged children.
  *
- * Possible returned errors are:
+ * Return: 0 on success, or -errno on failure.  Possible returned errors are:
  *
  * - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time;
  * - %EINVAL: @flags contains an unknown bit.

security/landlock/task.c

@@ -37,6 +37,9 @@
  *
  * Checks if the @parent domain is less or equal to (i.e. an ancestor, which
  * means a subset of) the @child domain.
+ *
+ * Return: True if @parent is an ancestor of or equal to @child, false
+ * otherwise.
  */
 static bool domain_scope_le(const struct landlock_ruleset *const parent,
 			    const struct landlock_ruleset *const child)
@@ -79,8 +82,7 @@ static int domain_ptrace(const struct landlock_ruleset *const parent,
  * If the current task has Landlock rules, then the child must have at least
  * the same rules.  Else denied.
  *
- * Determines whether a process may access another, returning 0 if permission
- * granted, -errno if denied.
+ * Return: 0 if permission is granted, -errno if denied.
  */
 static int hook_ptrace_access_check(struct task_struct *const child,
 				    const unsigned int mode)
@@ -129,8 +131,7 @@ static int hook_ptrace_access_check(struct task_struct *const child,
  * If the parent has Landlock rules, then the current task must have the same
  * or more rules.  Else denied.
  *
- * Determines whether the nominated task is permitted to trace the current
- * process, returning 0 if permission is granted, -errno if denied.
+ * Return: 0 if permission is granted, -errno if denied.
  */
 static int hook_ptrace_traceme(struct task_struct *const parent)
 {