LCOV - code coverage report
Current view: top level - security/landlock - fs.c (source / functions) Hit Total Coverage
Test: landlock.info Lines: 215 231 93.1 %
Date: 2021-04-07 12:34:12 Functions: 25 25 100.0 %

          Line data    Source code
       1             : // SPDX-License-Identifier: GPL-2.0-only
       2             : /*
       3             :  * Landlock LSM - Filesystem management and hooks
       4             :  *
       5             :  * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
       6             :  * Copyright © 2018-2020 ANSSI
       7             :  */
       8             : 
       9             : #include <linux/atomic.h>
      10             : #include <linux/bitops.h>
      11             : #include <linux/bits.h>
      12             : #include <linux/compiler_types.h>
      13             : #include <linux/dcache.h>
      14             : #include <linux/err.h>
      15             : #include <linux/fs.h>
      16             : #include <linux/init.h>
      17             : #include <linux/kernel.h>
      18             : #include <linux/limits.h>
      19             : #include <linux/list.h>
      20             : #include <linux/lsm_hooks.h>
      21             : #include <linux/mount.h>
      22             : #include <linux/namei.h>
      23             : #include <linux/path.h>
      24             : #include <linux/rcupdate.h>
      25             : #include <linux/spinlock.h>
      26             : #include <linux/stat.h>
      27             : #include <linux/types.h>
      28             : #include <linux/wait_bit.h>
      29             : #include <linux/workqueue.h>
      30             : #include <uapi/linux/landlock.h>
      31             : 
      32             : #include "common.h"
      33             : #include "cred.h"
      34             : #include "fs.h"
      35             : #include "limits.h"
      36             : #include "object.h"
      37             : #include "ruleset.h"
      38             : #include "setup.h"
      39             : 
      40             : /* Underlying object management */
      41             : 
      42          93 : static void release_inode(struct landlock_object *const object)
      43             :         __releases(object->lock)
      44             : {
      45          93 :         struct inode *const inode = object->underobj;
      46          93 :         struct super_block *sb;
      47             : 
      48          93 :         if (!inode) {
      49          87 :                 spin_unlock(&object->lock);
      50          87 :                 return;
      51             :         }
      52             : 
      53             :         /*
      54             :          * Protects against concurrent use by hook_sb_delete() of the reference
      55             :          * to the underlying inode.
      56             :          */
      57           6 :         object->underobj = NULL;
      58             :         /*
      59             :          * Makes sure that if the filesystem is concurrently unmounted,
      60             :          * hook_sb_delete() will wait for us to finish iput().
      61             :          */
      62           6 :         sb = inode->i_sb;
      63           6 :         atomic_long_inc(&landlock_superblock(sb)->inode_refs);
      64           6 :         spin_unlock(&object->lock);
      65             :         /*
      66             :          * Because object->underobj was not NULL, hook_sb_delete() and
      67             :          * get_inode_object() guarantee that it is safe to reset
      68             :          * landlock_inode(inode)->object while it is not NULL.  It is therefore
      69             :          * not necessary to lock inode->i_lock.
      70             :          */
      71           6 :         rcu_assign_pointer(landlock_inode(inode)->object, NULL);
      72             :         /*
      73             :          * Now, new rules can safely be tied to @inode with get_inode_object().
      74             :          */
      75             : 
      76           6 :         iput(inode);
      77          12 :         if (atomic_long_dec_and_test(&landlock_superblock(sb)->inode_refs))
      78           6 :                 wake_up_var(&landlock_superblock(sb)->inode_refs);
      79             : }
      80             : 
      81             : static const struct landlock_object_underops landlock_fs_underops = {
      82             :         .release = release_inode
      83             : };
      84             : 
      85             : /* Ruleset management */
      86             : 
      87         104 : static struct landlock_object *get_inode_object(struct inode *const inode)
      88             : {
      89         104 :         struct landlock_object *object, *new_object;
      90         104 :         struct landlock_inode_security *inode_sec = landlock_inode(inode);
      91             : 
      92         104 :         rcu_read_lock();
      93             : retry:
      94         104 :         object = rcu_dereference(inode_sec->object);
      95         104 :         if (object) {
      96          11 :                 if (likely(refcount_inc_not_zero(&object->usage))) {
      97          11 :                         rcu_read_unlock();
      98          11 :                         return object;
      99             :                 }
     100             :                 /*
     101             :                  * We are racing with release_inode(), the object is going
     102             :                  * away.  Wait for release_inode(), then retry.
     103             :                  */
     104           0 :                 spin_lock(&object->lock);
     105           0 :                 spin_unlock(&object->lock);
     106           0 :                 goto retry;
     107             :         }
     108          93 :         rcu_read_unlock();
     109             : 
     110             :         /*
     111             :          * If there is no object tied to @inode, then create a new one (without
     112             :          * holding any locks).
     113             :          */
     114          93 :         new_object = landlock_create_object(&landlock_fs_underops, inode);
     115          93 :         if (IS_ERR(new_object))
     116           0 :                 return new_object;
     117             : 
     118             :         /*
     119             :          * Protects against concurrent calls to get_inode_object() or
     120             :          * hook_sb_delete().
     121             :          */
     122          93 :         spin_lock(&inode->i_lock);
     123          93 :         if (unlikely(rcu_access_pointer(inode_sec->object))) {
     124             :                 /* Someone else just created the object, bail out and retry. */
     125           0 :                 spin_unlock(&inode->i_lock);
     126           0 :                 kfree(new_object);
     127             : 
     128           0 :                 rcu_read_lock();
     129           0 :                 goto retry;
     130             :         }
     131             : 
     132             :         /*
     133             :          * @inode will be released by hook_sb_delete() on its superblock
     134             :          * shutdown, or by release_inode() when no more ruleset references the
     135             :          * related object.
     136             :          */
     137          93 :         ihold(inode);
     138          93 :         rcu_assign_pointer(inode_sec->object, new_object);
     139          93 :         spin_unlock(&inode->i_lock);
     140          93 :         return new_object;
     141             : }
     142             : 
     143             : /* All access rights that can be tied to files. */
     144             : #define ACCESS_FILE ( \
     145             :         LANDLOCK_ACCESS_FS_EXECUTE | \
     146             :         LANDLOCK_ACCESS_FS_WRITE_FILE | \
     147             :         LANDLOCK_ACCESS_FS_READ_FILE)
     148             : 
     149             : /*
     150             :  * @path: Should have been checked by get_path_from_fd().
     151             :  */
     152         114 : int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
     153             :                 const struct path *const path, u32 access_rights)
     154             : {
     155         114 :         int err;
     156         114 :         struct landlock_object *object;
     157             : 
     158             :         /* Files only get access rights that make sense. */
     159         143 :         if (!d_is_dir(path->dentry) && (access_rights | ACCESS_FILE) !=
     160             :                         ACCESS_FILE)
     161             :                 return -EINVAL;
     162         104 :         if (WARN_ON_ONCE(ruleset->num_layers != 1))
     163             :                 return -EINVAL;
     164             : 
     165             :         /* Transforms relative access rights to absolute ones. */
     166         104 :         access_rights |= LANDLOCK_MASK_ACCESS_FS & ~ruleset->fs_access_masks[0];
     167         104 :         object = get_inode_object(d_backing_inode(path->dentry));
     168         104 :         if (IS_ERR(object))
     169           0 :                 return PTR_ERR(object);
     170         104 :         mutex_lock(&ruleset->lock);
     171         104 :         err = landlock_insert_rule(ruleset, object, access_rights);
     172         104 :         mutex_unlock(&ruleset->lock);
     173             :         /*
     174             :          * No need to check for an error because landlock_insert_rule()
     175             :          * increments the refcount for the new object if needed.
     176             :          */
     177         104 :         landlock_put_object(object);
     178         104 :         return err;
     179             : }
     180             : 
     181             : /* Access-control management */
     182             : 
     183        1808 : static inline u64 unmask_layers(
     184             :                 const struct landlock_ruleset *const domain,
     185             :                 const struct path *const path, const u32 access_request,
     186             :                 u64 layer_mask)
     187             : {
     188        1808 :         const struct landlock_rule *rule;
     189        1808 :         const struct inode *inode;
     190        1808 :         size_t i;
     191             : 
     192        1808 :         if (d_is_negative(path->dentry))
     193             :                 /* Ignore nonexistent leafs. */
     194             :                 return layer_mask;
     195        1808 :         inode = d_backing_inode(path->dentry);
     196        1808 :         rcu_read_lock();
     197        5424 :         rule = landlock_find_rule(domain,
     198        1808 :                         rcu_dereference(landlock_inode(inode)->object));
     199        1808 :         rcu_read_unlock();
     200        1808 :         if (!rule)
     201             :                 return layer_mask;
     202             : 
     203             :         /*
     204             :          * An access is granted if, for each policy layer, at least one rule
     205             :          * encountered on the pathwalk grants the requested accesses,
     206             :          * regardless of their position in the layer stack.  We must then check
     207             :          * the remaining layers for each inode, from the first added layer to
     208             :          * the last one.
     209             :          */
     210        1030 :         for (i = 0; i < rule->num_layers; i++) {
     211         663 :                 const struct landlock_layer *const layer = &rule->layers[i];
     212         663 :                 const u64 layer_level = BIT_ULL(layer->level - 1);
     213             : 
     214             :                 /* Checks that the layer grants access to the full request. */
     215         663 :                 if ((layer->access & access_request) == access_request) {
     216         571 :                         layer_mask &= ~layer_level;
     217             : 
     218         571 :                         if (layer_mask == 0)
     219             :                                 return layer_mask;
     220             :                 }
     221             :         }
     222             :         return layer_mask;
     223             : }
     224             : 
     225         444 : static int check_access_path(const struct landlock_ruleset *const domain,
     226             :                 const struct path *const path, u32 access_request)
     227             : {
     228         444 :         bool allowed = false;
     229         444 :         struct path walker_path;
     230         444 :         u64 layer_mask;
     231         444 :         size_t i;
     232             : 
     233             :         /* Make sure all layers can be checked. */
     234         444 :         BUILD_BUG_ON(BITS_PER_TYPE(layer_mask) < LANDLOCK_MAX_NUM_LAYERS);
     235             : 
     236         444 :         if (!access_request)
     237             :                 return 0;
     238         444 :         if (WARN_ON_ONCE(!domain || !path))
     239             :                 return 0;
     240             :         /*
     241             :          * Allows access to pseudo filesystems that will never be mountable
     242             :          * (e.g. sockfs, pipefs), but can still be reachable through
     243             :          * /proc/<pid>/fd/<file-descriptor> .
     244             :          */
     245         444 :         if ((path->dentry->d_sb->s_flags & SB_NOUSER) ||
     246         442 :                         (d_is_positive(path->dentry) &&
     247         442 :                          unlikely(IS_PRIVATE(d_backing_inode(path->dentry)))))
     248             :                 return 0;
     249         442 :         if (WARN_ON_ONCE(domain->num_layers < 1))
     250             :                 return -EACCES;
     251             : 
     252             :         /* Saves all layers handling a subset of requested accesses. */
     253             :         layer_mask = 0;
     254        1281 :         for (i = 0; i < domain->num_layers; i++) {
     255         839 :                 if (domain->fs_access_masks[i] & access_request)
     256         755 :                         layer_mask |= BIT_ULL(i);
     257             :         }
     258             :         /* An access request not handled by the domain is allowed. */
     259         442 :         if (layer_mask == 0)
     260             :                 return 0;
     261             : 
     262         401 :         walker_path = *path;
     263         401 :         path_get(&walker_path);
     264             :         /*
     265             :          * We need to walk through all the hierarchy to not miss any relevant
     266             :          * restriction.
     267             :          */
     268        3215 :         while (true) {
     269        1808 :                 struct dentry *parent_dentry;
     270             : 
     271        1808 :                 layer_mask = unmask_layers(domain, &walker_path,
     272             :                                 access_request, layer_mask);
     273        1808 :                 if (layer_mask == 0) {
     274             :                         /* Stops when a rule from each layer grants access. */
     275             :                         allowed = true;
     276             :                         break;
     277             :                 }
     278             : 
     279        1587 : jump_up:
     280        2040 :                 if (walker_path.dentry == walker_path.mnt->mnt_root) {
     281         632 :                         if (follow_up(&walker_path)) {
     282             :                                 /* Ignores hidden mount points. */
     283         453 :                                 goto jump_up;
     284             :                         } else {
     285             :                                 /*
     286             :                                  * Stops at the real root.  Denies access
     287             :                                  * because not all layers have granted access.
     288             :                                  */
     289             :                                 allowed = false;
     290             :                                 break;
     291             :                         }
     292             :                 }
     293        1408 :                 if (unlikely(IS_ROOT(walker_path.dentry))) {
     294             :                         /*
     295             :                          * Stops at disconnected root directories.  Only allows
     296             :                          * access to internal filesystems (e.g. nsfs, which is
     297             :                          * reachable through /proc/<pid>/ns/<namespace>).
     298             :                          */
     299           1 :                         allowed = !!(walker_path.mnt->mnt_flags & MNT_INTERNAL);
     300           1 :                         break;
     301             :                 }
     302        1407 :                 parent_dentry = dget_parent(walker_path.dentry);
     303        1407 :                 dput(walker_path.dentry);
     304        1407 :                 walker_path.dentry = parent_dentry;
     305             :         }
     306         401 :         path_put(&walker_path);
     307         401 :         return allowed ? 0 : -EACCES;
     308             : }
     309             : 
     310        2842 : static inline int current_check_access_path(const struct path *const path,
     311             :                 const u32 access_request)
     312             : {
     313        2842 :         const struct landlock_ruleset *const dom =
     314        2842 :                 landlock_get_current_domain();
     315             : 
     316        2842 :         if (!dom)
     317             :                 return 0;
     318          39 :         return check_access_path(dom, path, access_request);
     319             : }
     320             : 
     321             : /* Inode hooks */
     322             : 
     323        5274 : static void hook_inode_free_security(struct inode *const inode)
     324             : {
     325             :         /*
     326             :          * All inodes must already have been untied from their object by
     327             :          * release_inode() or hook_sb_delete().
     328             :          */
     329        5274 :         WARN_ON_ONCE(landlock_inode(inode)->object);
     330        5274 : }
     331             : 
     332             : /* Super-block hooks */
     333             : 
     334             : /*
     335             :  * Release the inodes used in a security policy.
     336             :  *
     337             :  * Cf. fsnotify_unmount_inodes() and invalidate_inodes()
     338             :  */
     339          98 : static void hook_sb_delete(struct super_block *const sb)
     340             : {
     341          98 :         struct inode *inode, *prev_inode = NULL;
     342             : 
     343          98 :         if (!landlock_initialized)
     344             :                 return;
     345             : 
     346          98 :         spin_lock(&sb->s_inode_list_lock);
     347         193 :         list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
     348          95 :                 struct landlock_object *object;
     349             : 
     350             :                 /* Only handles referenced inodes. */
     351          95 :                 if (!atomic_read(&inode->i_count))
     352           0 :                         continue;
     353             : 
     354             :                 /*
     355             :                  * Protects against concurrent modification of inode (e.g.
     356             :                  * from get_inode_object()).
     357             :                  */
     358          95 :                 spin_lock(&inode->i_lock);
     359             :                 /*
     360             :                  * Checks I_FREEING and I_WILL_FREE  to protect against a race
     361             :                  * condition when release_inode() just called iput(), which
     362             :                  * could lead to a NULL dereference of inode->security or a
     363             :                  * second call to iput() for the same Landlock object.  Also
     364             :                  * checks I_NEW because such inode cannot be tied to an object.
     365             :                  */
     366          95 :                 if (inode->i_state & (I_FREEING | I_WILL_FREE | I_NEW)) {
     367           0 :                         spin_unlock(&inode->i_lock);
     368           0 :                         continue;
     369             :                 }
     370             : 
     371          95 :                 rcu_read_lock();
     372          95 :                 object = rcu_dereference(landlock_inode(inode)->object);
     373          95 :                 if (!object) {
     374           8 :                         rcu_read_unlock();
     375           8 :                         spin_unlock(&inode->i_lock);
     376           8 :                         continue;
     377             :                 }
     378             :                 /* Keeps a reference to this inode until the next loop walk. */
     379          87 :                 __iget(inode);
     380          87 :                 spin_unlock(&inode->i_lock);
     381             : 
     382             :                 /*
     383             :                  * If there is no concurrent release_inode() ongoing, then we
     384             :                  * are in charge of calling iput() on this inode, otherwise we
     385             :                  * will just wait for it to finish.
     386             :                  */
     387          87 :                 spin_lock(&object->lock);
     388          87 :                 if (object->underobj == inode) {
     389          87 :                         object->underobj = NULL;
     390          87 :                         spin_unlock(&object->lock);
     391          87 :                         rcu_read_unlock();
     392             : 
     393             :                         /*
     394             :                          * Because object->underobj was not NULL,
     395             :                          * release_inode() and get_inode_object() guarantee
     396             :                          * that it is safe to reset
     397             :                          * landlock_inode(inode)->object while it is not NULL.
     398             :                          * It is therefore not necessary to lock inode->i_lock.
     399             :                          */
     400          87 :                         rcu_assign_pointer(landlock_inode(inode)->object, NULL);
     401             :                         /*
     402             :                          * At this point, we own the ihold() reference that was
     403             :                          * originally set up by get_inode_object() and the
     404             :                          * __iget() reference that we just set in this loop
     405             :                          * walk.  Therefore the following call to iput() will
     406             :                          * not sleep nor drop the inode because there is now at
     407             :                          * least two references to it.
     408             :                          */
     409          87 :                         iput(inode);
     410             :                 } else {
     411           0 :                         spin_unlock(&object->lock);
     412           0 :                         rcu_read_unlock();
     413             :                 }
     414             : 
     415          87 :                 if (prev_inode) {
     416             :                         /*
     417             :                          * At this point, we still own the __iget() reference
     418             :                          * that we just set in this loop walk.  Therefore we
     419             :                          * can drop the list lock and know that the inode won't
     420             :                          * disappear from under us until the next loop walk.
     421             :                          */
     422          45 :                         spin_unlock(&sb->s_inode_list_lock);
     423             :                         /*
     424             :                          * We can now actually put the inode reference from the
     425             :                          * previous loop walk, which is not needed anymore.
     426             :                          */
     427          45 :                         iput(prev_inode);
     428          45 :                         cond_resched();
     429         140 :                         spin_lock(&sb->s_inode_list_lock);
     430             :                 }
     431             :                 prev_inode = inode;
     432             :         }
     433          98 :         spin_unlock(&sb->s_inode_list_lock);
     434             : 
     435             :         /* Puts the inode reference from the last loop walk, if any. */
     436          98 :         if (prev_inode)
     437          42 :                 iput(prev_inode);
     438             :         /* Waits for pending iput() in release_inode(). */
     439          98 :         wait_var_event(&landlock_superblock(sb)->inode_refs, !atomic_long_read(
     440             :                                 &landlock_superblock(sb)->inode_refs));
     441             : }
     442             : 
     443             : /*
     444             :  * Because a Landlock security policy is defined according to the filesystem
     445             :  * topology (i.e. the mount namespace), changing it may grant access to files
     446             :  * not previously allowed.
     447             :  *
     448             :  * To make it simple, deny any filesystem topology modification by landlocked
     449             :  * processes.  Non-landlocked processes may still change the namespace of a
     450             :  * landlocked process, but this kind of threat must be handled by a system-wide
     451             :  * access-control security policy.
     452             :  *
     453             :  * This could be lifted in the future if Landlock can safely handle mount
     454             :  * namespace updates requested by a landlocked process.  Indeed, we could
     455             :  * update the current domain (which is currently read-only) by taking into
     456             :  * account the accesses of the source and the destination of a new mount point.
     457             :  * However, it would also require to make all the child domains dynamically
     458             :  * inherit these new constraints.  Anyway, for backward compatibility reasons,
     459             :  * a dedicated user space option would be required (e.g. as a ruleset flag).
     460             :  */
     461         250 : static int hook_sb_mount(const char *const dev_name,
     462             :                 const struct path *const path, const char *const type,
     463             :                 const unsigned long flags, void *const data)
     464             : {
     465         250 :         if (!landlock_get_current_domain())
     466         249 :                 return 0;
     467             :         return -EPERM;
     468             : }
     469             : 
     470           3 : static int hook_move_mount(const struct path *const from_path,
     471             :                 const struct path *const to_path)
     472             : {
     473           3 :         if (!landlock_get_current_domain())
     474           2 :                 return 0;
     475             :         return -EPERM;
     476             : }
     477             : 
     478             : /*
     479             :  * Removing a mount point may reveal a previously hidden file hierarchy, which
     480             :  * may then grant access to files, which may have previously been forbidden.
     481             :  */
     482         112 : static int hook_sb_umount(struct vfsmount *const mnt, const int flags)
     483             : {
     484         112 :         if (!landlock_get_current_domain())
     485         112 :                 return 0;
     486             :         return -EPERM;
     487             : }
     488             : 
     489           3 : static int hook_sb_remount(struct super_block *const sb, void *const mnt_opts)
     490             : {
     491           3 :         if (!landlock_get_current_domain())
     492           3 :                 return 0;
     493             :         return -EPERM;
     494             : }
     495             : 
     496             : /*
     497             :  * pivot_root(2), like mount(2), changes the current mount namespace.  It must
     498             :  * then be forbidden for a landlocked process.
     499             :  *
     500             :  * However, chroot(2) may be allowed because it only changes the relative root
     501             :  * directory of the current process.  Moreover, it can be used to restrict the
     502             :  * view of the filesystem.
     503             :  */
     504           2 : static int hook_sb_pivotroot(const struct path *const old_path,
     505             :                 const struct path *const new_path)
     506             : {
     507           2 :         if (!landlock_get_current_domain())
     508           1 :                 return 0;
     509             :         return -EPERM;
     510             : }
     511             : 
     512             : /* Path hooks */
     513             : 
     514          81 : static inline u32 get_mode_access(const umode_t mode)
     515             : {
     516          81 :         switch (mode & S_IFMT) {
     517             :         case S_IFLNK:
     518             :                 return LANDLOCK_ACCESS_FS_MAKE_SYM;
     519          32 :         case 0:
     520             :                 /* A zero mode translates to S_IFREG. */
     521             :         case S_IFREG:
     522          32 :                 return LANDLOCK_ACCESS_FS_MAKE_REG;
     523           7 :         case S_IFDIR:
     524           7 :                 return LANDLOCK_ACCESS_FS_MAKE_DIR;
     525           9 :         case S_IFCHR:
     526           9 :                 return LANDLOCK_ACCESS_FS_MAKE_CHAR;
     527           9 :         case S_IFBLK:
     528           9 :                 return LANDLOCK_ACCESS_FS_MAKE_BLOCK;
     529           9 :         case S_IFIFO:
     530           9 :                 return LANDLOCK_ACCESS_FS_MAKE_FIFO;
     531           9 :         case S_IFSOCK:
     532           9 :                 return LANDLOCK_ACCESS_FS_MAKE_SOCK;
     533             :         default:
     534           0 :                 WARN_ON_ONCE(1);
     535           0 :                 return 0;
     536             :         }
     537             : }
     538             : 
     539             : /*
     540             :  * Creating multiple links or renaming may lead to privilege escalations if not
     541             :  * handled properly.  Indeed, we must be sure that the source doesn't gain more
     542             :  * privileges by being accessible from the destination.  This is getting more
     543             :  * complex when dealing with multiple layers.  The whole picture can be seen as
     544             :  * a multilayer partial ordering problem.  A future version of Landlock will
     545             :  * deal with that.
     546             :  */
     547          26 : static int hook_path_link(struct dentry *const old_dentry,
     548             :                 const struct path *const new_dir,
     549             :                 struct dentry *const new_dentry)
     550             : {
     551          26 :         const struct landlock_ruleset *const dom =
     552          26 :                 landlock_get_current_domain();
     553             : 
     554          26 :         if (!dom)
     555             :                 return 0;
     556             :         /* The mount points are the same for old and new paths, cf. EXDEV. */
     557          26 :         if (old_dentry->d_parent != new_dir->dentry)
     558             :                 /* Gracefully forbids reparenting. */
     559             :                 return -EXDEV;
     560          24 :         if (unlikely(d_is_negative(old_dentry)))
     561             :                 return -ENOENT;
     562          24 :         return check_access_path(dom, new_dir,
     563          24 :                         get_mode_access(d_backing_inode(old_dentry)->i_mode));
     564             : }
     565             : 
     566          70 : static inline u32 maybe_remove(const struct dentry *const dentry)
     567             : {
     568          70 :         if (d_is_negative(dentry))
     569             :                 return 0;
     570          85 :         return d_is_dir(dentry) ? LANDLOCK_ACCESS_FS_REMOVE_DIR :
     571             :                 LANDLOCK_ACCESS_FS_REMOVE_FILE;
     572             : }
     573             : 
     574         370 : static int hook_path_rename(const struct path *const old_dir,
     575             :                 struct dentry *const old_dentry,
     576             :                 const struct path *const new_dir,
     577             :                 struct dentry *const new_dentry)
     578             : {
     579         370 :         const struct landlock_ruleset *const dom =
     580         370 :                 landlock_get_current_domain();
     581             : 
     582         370 :         if (!dom)
     583             :                 return 0;
     584             :         /* The mount points are the same for old and new paths, cf. EXDEV. */
     585          46 :         if (old_dir->dentry != new_dir->dentry)
     586             :                 /* Gracefully forbids reparenting. */
     587             :                 return -EXDEV;
     588          35 :         if (unlikely(d_is_negative(old_dentry)))
     589             :                 return -ENOENT;
     590             :         /* RENAME_EXCHANGE is handled because directories are the same. */
     591          35 :         return check_access_path(dom, old_dir, maybe_remove(old_dentry) |
     592          35 :                         maybe_remove(new_dentry) |
     593          35 :                         get_mode_access(d_backing_inode(old_dentry)->i_mode));
     594             : }
     595             : 
     596         786 : static int hook_path_mkdir(const struct path *const dir,
     597             :                 struct dentry *const dentry, const umode_t mode)
     598             : {
     599         786 :         return current_check_access_path(dir, LANDLOCK_ACCESS_FS_MAKE_DIR);
     600             : }
     601             : 
     602        1330 : static int hook_path_mknod(const struct path *const dir,
     603             :                 struct dentry *const dentry, const umode_t mode,
     604             :                 const unsigned int dev)
     605             : {
     606        1330 :         const struct landlock_ruleset *const dom =
     607        1330 :                 landlock_get_current_domain();
     608             : 
     609        1330 :         if (!dom)
     610             :                 return 0;
     611          22 :         return check_access_path(dom, dir, get_mode_access(mode));
     612             : }
     613             : 
     614         210 : static int hook_path_symlink(const struct path *const dir,
     615             :                 struct dentry *const dentry, const char *const old_name)
     616             : {
     617         210 :         return current_check_access_path(dir, LANDLOCK_ACCESS_FS_MAKE_SYM);
     618             : }
     619             : 
     620         776 : static int hook_path_unlink(const struct path *const dir,
     621             :                 struct dentry *const dentry)
     622             : {
     623         776 :         return current_check_access_path(dir, LANDLOCK_ACCESS_FS_REMOVE_FILE);
     624             : }
     625             : 
     626        1070 : static int hook_path_rmdir(const struct path *const dir,
     627             :                 struct dentry *const dentry)
     628             : {
     629        1070 :         return current_check_access_path(dir, LANDLOCK_ACCESS_FS_REMOVE_DIR);
     630             : }
     631             : 
     632             : /* File hooks */
     633             : 
     634         324 : static inline u32 get_file_access(const struct file *const file)
     635             : {
     636         324 :         u32 access = 0;
     637             : 
     638         324 :         if (file->f_mode & FMODE_READ) {
     639             :                 /* A directory can only be opened in read mode. */
     640         268 :                 if (S_ISDIR(file_inode(file)->i_mode))
     641             :                         return LANDLOCK_ACCESS_FS_READ_DIR;
     642             :                 access = LANDLOCK_ACCESS_FS_READ_FILE;
     643             :         }
     644         200 :         if (file->f_mode & FMODE_WRITE)
     645         112 :                 access |= LANDLOCK_ACCESS_FS_WRITE_FILE;
     646             :         /* __FMODE_EXEC is indeed part of f_flags, not f_mode. */
     647         200 :         if (file->f_flags & __FMODE_EXEC)
     648           3 :                 access |= LANDLOCK_ACCESS_FS_EXECUTE;
     649             :         return access;
     650             : }
     651             : 
     652       17697 : static int hook_file_open(struct file *const file)
     653             : {
     654       17697 :         const struct landlock_ruleset *const dom =
     655       17697 :                 landlock_get_current_domain();
     656             : 
     657       17702 :         if (!dom)
     658             :                 return 0;
     659             :         /*
     660             :          * Because a file may be opened with O_PATH, get_file_access() may
     661             :          * return 0.  This case will be handled with a future Landlock
     662             :          * evolution.
     663             :          */
     664         324 :         return check_access_path(dom, &file->f_path, get_file_access(file));
     665             : }
     666             : 
     667             : static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = {
     668             :         LSM_HOOK_INIT(inode_free_security, hook_inode_free_security),
     669             : 
     670             :         LSM_HOOK_INIT(sb_delete, hook_sb_delete),
     671             :         LSM_HOOK_INIT(sb_mount, hook_sb_mount),
     672             :         LSM_HOOK_INIT(move_mount, hook_move_mount),
     673             :         LSM_HOOK_INIT(sb_umount, hook_sb_umount),
     674             :         LSM_HOOK_INIT(sb_remount, hook_sb_remount),
     675             :         LSM_HOOK_INIT(sb_pivotroot, hook_sb_pivotroot),
     676             : 
     677             :         LSM_HOOK_INIT(path_link, hook_path_link),
     678             :         LSM_HOOK_INIT(path_rename, hook_path_rename),
     679             :         LSM_HOOK_INIT(path_mkdir, hook_path_mkdir),
     680             :         LSM_HOOK_INIT(path_mknod, hook_path_mknod),
     681             :         LSM_HOOK_INIT(path_symlink, hook_path_symlink),
     682             :         LSM_HOOK_INIT(path_unlink, hook_path_unlink),
     683             :         LSM_HOOK_INIT(path_rmdir, hook_path_rmdir),
     684             : 
     685             :         LSM_HOOK_INIT(file_open, hook_file_open),
     686             : };
     687             : 
     688           1 : __init void landlock_add_fs_hooks(void)
     689             : {
     690           1 :         security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
     691             :                         LANDLOCK_NAME);
     692           1 : }

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