fs.h

  1/* SPDX-License-Identifier: GPL-2.0-only */
  2/*
  3 * Landlock - Filesystem management and hooks
  4 *
  5 * Copyright © 2017-2020 Mickaël Salaün <mic@digikod.net>
  6 * Copyright © 2018-2020 ANSSI
  7 * Copyright © 2024-2025 Microsoft Corporation
  8 */
  9
 10#ifndef _SECURITY_LANDLOCK_FS_H
 11#define _SECURITY_LANDLOCK_FS_H
 12
 13#include <linux/build_bug.h>
 14#include <linux/fs.h>
 15#include <linux/init.h>
 16#include <linux/rcupdate.h>
 17
 18#include "access.h"
 19#include "cred.h"
 20#include "ruleset.h"
 21#include "setup.h"
 22
 23/**
 24 * struct landlock_inode_security - Inode security blob
 25 *
 26 * Enable to reference a &struct landlock_object tied to an inode (i.e.
 27 * underlying object).
 28 */
 29struct landlock_inode_security {
 30	/**
 31	 * @object: Weak pointer to an allocated object.  All assignments of a
 32	 * new object are protected by the underlying inode->i_lock.  However,
 33	 * atomically disassociating @object from the inode is only protected
 34	 * by @object->lock, from the time @object's usage refcount drops to
 35	 * zero to the time this pointer is nulled out (cf. release_inode() and
 36	 * hook_sb_delete()).  Indeed, such disassociation doesn't require
 37	 * inode->i_lock thanks to the careful rcu_access_pointer() check
 38	 * performed by get_inode_object().
 39	 */
 40	struct landlock_object __rcu *object;
 41};
 42
 43/**
 44 * struct landlock_file_security - File security blob
 45 *
 46 * This information is populated when opening a file in hook_file_open, and
 47 * tracks the relevant Landlock access rights that were available at the time
 48 * of opening the file. Other LSM hooks use these rights in order to authorize
 49 * operations on already opened files.
 50 */
 51struct landlock_file_security {
 52	/**
 53	 * @allowed_access: Access rights that were available at the time of
 54	 * opening the file. This is not necessarily the full set of access
 55	 * rights available at that time, but it's the necessary subset as
 56	 * needed to authorize later operations on the open file.
 57	 */
 58	access_mask_t allowed_access;
 59
 60#ifdef CONFIG_AUDIT
 61	/**
 62	 * @deny_masks: Domain layer levels that deny an optional access (see
 63	 * _LANDLOCK_ACCESS_FS_OPTIONAL).
 64	 */
 65	deny_masks_t deny_masks;
 66	/**
 67	 * @fown_layer: Layer level of @fown_subject->domain with
 68	 * LANDLOCK_SCOPE_SIGNAL.
 69	 */
 70	u8 fown_layer;
 71#endif /* CONFIG_AUDIT */
 72
 73	/**
 74	 * @fown_subject: Landlock credential of the task that set the PID that
 75	 * may receive a signal e.g., SIGURG when writing MSG_OOB to the
 76	 * related socket.  This pointer is protected by the related
 77	 * file->f_owner->lock, as for fown_struct's members: pid, uid, and
 78	 * euid.
 79	 */
 80	struct landlock_cred_security fown_subject;
 81};
 82
 83#ifdef CONFIG_AUDIT
 84
 85/* Makes sure all layers can be identified. */
 86/* clang-format off */
 87static_assert((typeof_member(struct landlock_file_security, fown_layer))~0 >=
 88	      LANDLOCK_MAX_NUM_LAYERS);
 89/* clang-format off */
 90
 91#endif /* CONFIG_AUDIT */
 92
 93/**
 94 * struct landlock_superblock_security - Superblock security blob
 95 *
 96 * Enable hook_sb_delete() to wait for concurrent calls to release_inode().
 97 */
 98struct landlock_superblock_security {
 99	/**
100	 * @inode_refs: Number of pending inodes (from this superblock) that
101	 * are being released by release_inode().
102	 * Cf. struct super_block->s_fsnotify_inode_refs .
103	 */
104	atomic_long_t inode_refs;
105};
106
107static inline struct landlock_file_security *
108landlock_file(const struct file *const file)
109{
110	return file->f_security + landlock_blob_sizes.lbs_file;
111}
112
113static inline struct landlock_inode_security *
114landlock_inode(const struct inode *const inode)
115{
116	return inode->i_security + landlock_blob_sizes.lbs_inode;
117}
118
119static inline struct landlock_superblock_security *
120landlock_superblock(const struct super_block *const superblock)
121{
122	return superblock->s_security + landlock_blob_sizes.lbs_superblock;
123}
124
125__init void landlock_add_fs_hooks(void);
126
127int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
128			    const struct path *const path,
129			    access_mask_t access_hierarchy);
130
131#endif /* _SECURITY_LANDLOCK_FS_H */