security/landlock/fs.h

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