security/landlock/fs.h

root/security/landlock/fs.h
/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Landlock - Filesystem management and hooks
 *
 * Copyright © 2017-2020 Mickaël Salaün <mic@digikod.net>
 * Copyright © 2018-2020 ANSSI
 * Copyright © 2024-2025 Microsoft Corporation
 */

#ifndef _SECURITY_LANDLOCK_FS_H
#define _SECURITY_LANDLOCK_FS_H

#include <linux/build_bug.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/rcupdate.h>

#include "access.h"
#include "cred.h"
#include "ruleset.h"
#include "setup.h"

/**
 * struct landlock_inode_security - Inode security blob
 *
 * Enable to reference a &struct landlock_object tied to an inode (i.e.
 * underlying object).
 */
struct landlock_inode_security {
        /**
         * @object: Weak pointer to an allocated object.  All assignments of a
         * new object are protected by the underlying inode->i_lock.  However,
         * atomically disassociating @object from the inode is only protected
         * by @object->lock, from the time @object's usage refcount drops to
         * zero to the time this pointer is nulled out (cf. release_inode() and
         * hook_sb_delete()).  Indeed, such disassociation doesn't require
         * inode->i_lock thanks to the careful rcu_access_pointer() check
         * performed by get_inode_object().
         */
        struct landlock_object __rcu *object;
};

/**
 * struct landlock_file_security - File security blob
 *
 * This information is populated when opening a file in hook_file_open, and
 * tracks the relevant Landlock access rights that were available at the time
 * of opening the file. Other LSM hooks use these rights in order to authorize
 * operations on already opened files.
 */
struct landlock_file_security {
        /**
         * @allowed_access: Access rights that were available at the time of
         * opening the file. This is not necessarily the full set of access
         * rights available at that time, but it's the necessary subset as
         * needed to authorize later operations on the open file.
         */
        access_mask_t allowed_access;

#ifdef CONFIG_AUDIT
        /**
         * @deny_masks: Domain layer levels that deny an optional access (see
         * _LANDLOCK_ACCESS_FS_OPTIONAL).
         */
        deny_masks_t deny_masks;
        /**
         * @fown_layer: Layer level of @fown_subject->domain with
         * LANDLOCK_SCOPE_SIGNAL.
         */
        u8 fown_layer;
#endif /* CONFIG_AUDIT */

        /**
         * @fown_subject: Landlock credential of the task that set the PID that
         * may receive a signal e.g., SIGURG when writing MSG_OOB to the
         * related socket.  This pointer is protected by the related
         * file->f_owner->lock, as for fown_struct's members: pid, uid, and
         * euid.
         */
        struct landlock_cred_security fown_subject;
};

#ifdef CONFIG_AUDIT

/* Makes sure all layers can be identified. */
/* clang-format off */
static_assert((typeof_member(struct landlock_file_security, fown_layer))~0 >=
              LANDLOCK_MAX_NUM_LAYERS);
/* clang-format off */

#endif /* CONFIG_AUDIT */

/**
 * struct landlock_superblock_security - Superblock security blob
 *
 * Enable hook_sb_delete() to wait for concurrent calls to release_inode().
 */
struct landlock_superblock_security {
        /**
         * @inode_refs: Number of pending inodes (from this superblock) that
         * are being released by release_inode().
         * Cf. struct super_block->s_fsnotify_inode_refs .
         */
        atomic_long_t inode_refs;
};

static inline struct landlock_file_security *
landlock_file(const struct file *const file)
{
        return file->f_security + landlock_blob_sizes.lbs_file;
}

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)
{
        return superblock->s_security + landlock_blob_sizes.lbs_superblock;
}

__init void landlock_add_fs_hooks(void);

int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
                            const struct path *const path,
                            access_mask_t access_hierarchy);

#endif /* _SECURITY_LANDLOCK_FS_H */
Linux
