diff options
Diffstat (limited to 'security/landlock/fs.c')
| -rw-r--r-- | security/landlock/fs.c | 323 |
1 files changed, 250 insertions, 73 deletions
diff --git a/security/landlock/fs.c b/security/landlock/fs.c index 71b9dc331aae..6fee7c20f64d 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -1,10 +1,10 @@ // SPDX-License-Identifier: GPL-2.0-only /* - * Landlock LSM - Filesystem management and hooks + * Landlock - Filesystem management and hooks * * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net> * Copyright © 2018-2020 ANSSI - * Copyright © 2021-2022 Microsoft Corporation + * Copyright © 2021-2025 Microsoft Corporation * Copyright © 2022 Günther Noack <gnoack3000@gmail.com> * Copyright © 2023-2024 Google LLC */ @@ -23,11 +23,14 @@ #include <linux/kernel.h> #include <linux/limits.h> #include <linux/list.h> +#include <linux/lsm_audit.h> #include <linux/lsm_hooks.h> #include <linux/mount.h> #include <linux/namei.h> #include <linux/path.h> +#include <linux/pid.h> #include <linux/rcupdate.h> +#include <linux/sched/signal.h> #include <linux/spinlock.h> #include <linux/stat.h> #include <linux/types.h> @@ -37,8 +40,10 @@ #include <uapi/linux/landlock.h> #include "access.h" +#include "audit.h" #include "common.h" #include "cred.h" +#include "domain.h" #include "fs.h" #include "limits.h" #include "object.h" @@ -393,12 +398,6 @@ static const struct access_masks any_fs = { .fs = ~0, }; -static const struct landlock_ruleset *get_current_fs_domain(void) -{ - return landlock_get_applicable_domain(landlock_get_current_domain(), - any_fs); -} - /* * Check that a destination file hierarchy has more restrictions than a source * file hierarchy. This is only used for link and rename actions. @@ -728,6 +727,7 @@ static void test_is_eacces_with_write(struct kunit *const test) * those identified by @access_request_parent1). This matrix can * initially refer to domain layer masks and, when the accesses for the * destination and source are the same, to requested layer masks. + * @log_request_parent1: Audit request to fill if the related access is denied. * @dentry_child1: Dentry to the initial child of the parent1 path. This * pointer must be NULL for non-refer actions (i.e. not link nor rename). * @access_request_parent2: Similar to @access_request_parent1 but for a @@ -736,6 +736,7 @@ static void test_is_eacces_with_write(struct kunit *const test) * the source. Must be set to 0 when using a simple path request. * @layer_masks_parent2: Similar to @layer_masks_parent1 but for a refer * action. This must be NULL otherwise. + * @log_request_parent2: Audit request to fill if the related access is denied. * @dentry_child2: Dentry to the initial child of the parent2 path. This * pointer is only set for RENAME_EXCHANGE actions and must be NULL * otherwise. @@ -755,10 +756,12 @@ static bool is_access_to_paths_allowed( const struct path *const path, const access_mask_t access_request_parent1, layer_mask_t (*const layer_masks_parent1)[LANDLOCK_NUM_ACCESS_FS], - const struct dentry *const dentry_child1, + struct landlock_request *const log_request_parent1, + struct dentry *const dentry_child1, const access_mask_t access_request_parent2, layer_mask_t (*const layer_masks_parent2)[LANDLOCK_NUM_ACCESS_FS], - const struct dentry *const dentry_child2) + struct landlock_request *const log_request_parent2, + struct dentry *const dentry_child2) { bool allowed_parent1 = false, allowed_parent2 = false, is_dom_check, child1_is_directory = true, child2_is_directory = true; @@ -771,11 +774,14 @@ static bool is_access_to_paths_allowed( if (!access_request_parent1 && !access_request_parent2) return true; - if (WARN_ON_ONCE(!domain || !path)) + + if (WARN_ON_ONCE(!path)) return true; + if (is_nouser_or_private(path->dentry)) return true; - if (WARN_ON_ONCE(domain->num_layers < 1 || !layer_masks_parent1)) + + if (WARN_ON_ONCE(!layer_masks_parent1)) return false; allowed_parent1 = is_layer_masks_allowed(layer_masks_parent1); @@ -920,24 +926,51 @@ jump_up: } path_put(&walker_path); + if (!allowed_parent1) { + log_request_parent1->type = LANDLOCK_REQUEST_FS_ACCESS; + log_request_parent1->audit.type = LSM_AUDIT_DATA_PATH; + log_request_parent1->audit.u.path = *path; + log_request_parent1->access = access_masked_parent1; + log_request_parent1->layer_masks = layer_masks_parent1; + log_request_parent1->layer_masks_size = + ARRAY_SIZE(*layer_masks_parent1); + } + + if (!allowed_parent2) { + log_request_parent2->type = LANDLOCK_REQUEST_FS_ACCESS; + log_request_parent2->audit.type = LSM_AUDIT_DATA_PATH; + log_request_parent2->audit.u.path = *path; + log_request_parent2->access = access_masked_parent2; + log_request_parent2->layer_masks = layer_masks_parent2; + log_request_parent2->layer_masks_size = + ARRAY_SIZE(*layer_masks_parent2); + } return allowed_parent1 && allowed_parent2; } static int current_check_access_path(const struct path *const path, access_mask_t access_request) { - const struct landlock_ruleset *const dom = get_current_fs_domain(); + const struct access_masks masks = { + .fs = access_request, + }; + const struct landlock_cred_security *const subject = + landlock_get_applicable_subject(current_cred(), masks, NULL); layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {}; + struct landlock_request request = {}; - if (!dom) + if (!subject) return 0; - access_request = landlock_init_layer_masks( - dom, access_request, &layer_masks, LANDLOCK_KEY_INODE); - if (is_access_to_paths_allowed(dom, path, access_request, &layer_masks, - NULL, 0, NULL, NULL)) + access_request = landlock_init_layer_masks(subject->domain, + access_request, &layer_masks, + LANDLOCK_KEY_INODE); + if (is_access_to_paths_allowed(subject->domain, path, access_request, + &layer_masks, &request, NULL, 0, NULL, + NULL, NULL)) return 0; + landlock_log_denial(subject, &request); return -EACCES; } @@ -1098,18 +1131,19 @@ static int current_check_refer_path(struct dentry *const old_dentry, struct dentry *const new_dentry, const bool removable, const bool exchange) { - const struct landlock_ruleset *const dom = get_current_fs_domain(); + const struct landlock_cred_security *const subject = + landlock_get_applicable_subject(current_cred(), any_fs, NULL); bool allow_parent1, allow_parent2; access_mask_t access_request_parent1, access_request_parent2; struct path mnt_dir; struct dentry *old_parent; layer_mask_t layer_masks_parent1[LANDLOCK_NUM_ACCESS_FS] = {}, layer_masks_parent2[LANDLOCK_NUM_ACCESS_FS] = {}; + struct landlock_request request1 = {}, request2 = {}; - if (!dom) + if (!subject) return 0; - if (WARN_ON_ONCE(dom->num_layers < 1)) - return -EACCES; + if (unlikely(d_is_negative(old_dentry))) return -ENOENT; if (exchange) { @@ -1134,12 +1168,16 @@ static int current_check_refer_path(struct dentry *const old_dentry, * for same-directory referer (i.e. no reparenting). */ access_request_parent1 = landlock_init_layer_masks( - dom, access_request_parent1 | access_request_parent2, + subject->domain, + access_request_parent1 | access_request_parent2, &layer_masks_parent1, LANDLOCK_KEY_INODE); - if (is_access_to_paths_allowed( - dom, new_dir, access_request_parent1, - &layer_masks_parent1, NULL, 0, NULL, NULL)) + if (is_access_to_paths_allowed(subject->domain, new_dir, + access_request_parent1, + &layer_masks_parent1, &request1, + NULL, 0, NULL, NULL, NULL)) return 0; + + landlock_log_denial(subject, &request1); return -EACCES; } @@ -1160,10 +1198,12 @@ static int current_check_refer_path(struct dentry *const old_dentry, old_dentry->d_parent; /* new_dir->dentry is equal to new_dentry->d_parent */ - allow_parent1 = collect_domain_accesses(dom, mnt_dir.dentry, old_parent, + allow_parent1 = collect_domain_accesses(subject->domain, mnt_dir.dentry, + old_parent, &layer_masks_parent1); - allow_parent2 = collect_domain_accesses( - dom, mnt_dir.dentry, new_dir->dentry, &layer_masks_parent2); + allow_parent2 = collect_domain_accesses(subject->domain, mnt_dir.dentry, + new_dir->dentry, + &layer_masks_parent2); if (allow_parent1 && allow_parent2) return 0; @@ -1175,11 +1215,21 @@ static int current_check_refer_path(struct dentry *const old_dentry, * destination parent access rights. */ if (is_access_to_paths_allowed( - dom, &mnt_dir, access_request_parent1, &layer_masks_parent1, - old_dentry, access_request_parent2, &layer_masks_parent2, + subject->domain, &mnt_dir, access_request_parent1, + &layer_masks_parent1, &request1, old_dentry, + access_request_parent2, &layer_masks_parent2, &request2, exchange ? new_dentry : NULL)) return 0; + if (request1.access) { + request1.audit.u.path.dentry = old_parent; + landlock_log_denial(subject, &request1); + } + if (request2.access) { + request2.audit.u.path.dentry = new_dir->dentry; + landlock_log_denial(subject, &request2); + } + /* * This prioritizes EACCES over EXDEV for all actions, including * renames with RENAME_EXCHANGE. @@ -1216,7 +1266,7 @@ static void hook_inode_free_security_rcu(void *inode_security) /* * Release the inodes used in a security policy. * - * Cf. fsnotify_unmount_inodes() and invalidate_inodes() + * Cf. fsnotify_unmount_inodes() and evict_inodes() */ static void hook_sb_delete(struct super_block *const sb) { @@ -1322,6 +1372,34 @@ static void hook_sb_delete(struct super_block *const sb) !atomic_long_read(&landlock_superblock(sb)->inode_refs)); } +static void +log_fs_change_topology_path(const struct landlock_cred_security *const subject, + size_t handle_layer, const struct path *const path) +{ + landlock_log_denial(subject, &(struct landlock_request) { + .type = LANDLOCK_REQUEST_FS_CHANGE_TOPOLOGY, + .audit = { + .type = LSM_AUDIT_DATA_PATH, + .u.path = *path, + }, + .layer_plus_one = handle_layer + 1, + }); +} + +static void log_fs_change_topology_dentry( + const struct landlock_cred_security *const subject, size_t handle_layer, + struct dentry *const dentry) +{ + landlock_log_denial(subject, &(struct landlock_request) { + .type = LANDLOCK_REQUEST_FS_CHANGE_TOPOLOGY, + .audit = { + .type = LSM_AUDIT_DATA_DENTRY, + .u.dentry = dentry, + }, + .layer_plus_one = handle_layer + 1, + }); +} + /* * Because a Landlock security policy is defined according to the filesystem * topology (i.e. the mount namespace), changing it may grant access to files @@ -1344,16 +1422,30 @@ static int hook_sb_mount(const char *const dev_name, const struct path *const path, const char *const type, const unsigned long flags, void *const data) { - if (!get_current_fs_domain()) + size_t handle_layer; + const struct landlock_cred_security *const subject = + landlock_get_applicable_subject(current_cred(), any_fs, + &handle_layer); + + if (!subject) return 0; + + log_fs_change_topology_path(subject, handle_layer, path); return -EPERM; } static int hook_move_mount(const struct path *const from_path, const struct path *const to_path) { - if (!get_current_fs_domain()) + size_t handle_layer; + const struct landlock_cred_security *const subject = + landlock_get_applicable_subject(current_cred(), any_fs, + &handle_layer); + + if (!subject) return 0; + + log_fs_change_topology_path(subject, handle_layer, to_path); return -EPERM; } @@ -1363,15 +1455,29 @@ static int hook_move_mount(const struct path *const from_path, */ static int hook_sb_umount(struct vfsmount *const mnt, const int flags) { - if (!get_current_fs_domain()) + size_t handle_layer; + const struct landlock_cred_security *const subject = + landlock_get_applicable_subject(current_cred(), any_fs, + &handle_layer); + + if (!subject) return 0; + + log_fs_change_topology_dentry(subject, handle_layer, mnt->mnt_root); return -EPERM; } static int hook_sb_remount(struct super_block *const sb, void *const mnt_opts) { - if (!get_current_fs_domain()) + size_t handle_layer; + const struct landlock_cred_security *const subject = + landlock_get_applicable_subject(current_cred(), any_fs, + &handle_layer); + + if (!subject) return 0; + + log_fs_change_topology_dentry(subject, handle_layer, sb->s_root); return -EPERM; } @@ -1386,8 +1492,15 @@ static int hook_sb_remount(struct super_block *const sb, void *const mnt_opts) static int hook_sb_pivotroot(const struct path *const old_path, const struct path *const new_path) { - if (!get_current_fs_domain()) + size_t handle_layer; + const struct landlock_cred_security *const subject = + landlock_get_applicable_subject(current_cred(), any_fs, + &handle_layer); + + if (!subject) return 0; + + log_fs_change_topology_path(subject, handle_layer, new_path); return -EPERM; } @@ -1504,11 +1617,11 @@ static int hook_file_open(struct file *const file) layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {}; access_mask_t open_access_request, full_access_request, allowed_access, optional_access; - const struct landlock_ruleset *const dom = - landlock_get_applicable_domain( - landlock_cred(file->f_cred)->domain, any_fs); + const struct landlock_cred_security *const subject = + landlock_get_applicable_subject(file->f_cred, any_fs, NULL); + struct landlock_request request = {}; - if (!dom) + if (!subject) return 0; /* @@ -1529,10 +1642,11 @@ static int hook_file_open(struct file *const file) full_access_request = open_access_request | optional_access; if (is_access_to_paths_allowed( - dom, &file->f_path, - landlock_init_layer_masks(dom, full_access_request, - &layer_masks, LANDLOCK_KEY_INODE), - &layer_masks, NULL, 0, NULL, NULL)) { + subject->domain, &file->f_path, + landlock_init_layer_masks(subject->domain, + full_access_request, &layer_masks, + LANDLOCK_KEY_INODE), + &layer_masks, &request, NULL, 0, NULL, NULL, NULL)) { allowed_access = full_access_request; } else { unsigned long access_bit; @@ -1558,10 +1672,18 @@ static int hook_file_open(struct file *const file) * file access rights in the opened struct file. */ landlock_file(file)->allowed_access = allowed_access; +#ifdef CONFIG_AUDIT + landlock_file(file)->deny_masks = landlock_get_deny_masks( + _LANDLOCK_ACCESS_FS_OPTIONAL, optional_access, &layer_masks, + ARRAY_SIZE(layer_masks)); +#endif /* CONFIG_AUDIT */ if ((open_access_request & allowed_access) == open_access_request) return 0; + /* Sets access to reflect the actual request. */ + request.access = open_access_request; + landlock_log_denial(subject, &request); return -EACCES; } @@ -1579,11 +1701,24 @@ static int hook_file_truncate(struct file *const file) */ if (landlock_file(file)->allowed_access & LANDLOCK_ACCESS_FS_TRUNCATE) return 0; + + landlock_log_denial(landlock_cred(file->f_cred), &(struct landlock_request) { + .type = LANDLOCK_REQUEST_FS_ACCESS, + .audit = { + .type = LSM_AUDIT_DATA_FILE, + .u.file = file, + }, + .all_existing_optional_access = _LANDLOCK_ACCESS_FS_OPTIONAL, + .access = LANDLOCK_ACCESS_FS_TRUNCATE, +#ifdef CONFIG_AUDIT + .deny_masks = landlock_file(file)->deny_masks, +#endif /* CONFIG_AUDIT */ + }); return -EACCES; } -static int hook_file_ioctl(struct file *file, unsigned int cmd, - unsigned long arg) +static int hook_file_ioctl_common(const struct file *const file, + const unsigned int cmd, const bool is_compat) { access_mask_t allowed_access = landlock_file(file)->allowed_access; @@ -1599,56 +1734,98 @@ static int hook_file_ioctl(struct file *file, unsigned int cmd, if (!is_device(file)) return 0; - if (is_masked_device_ioctl(cmd)) + if (unlikely(is_compat) ? is_masked_device_ioctl_compat(cmd) : + is_masked_device_ioctl(cmd)) return 0; + landlock_log_denial(landlock_cred(file->f_cred), &(struct landlock_request) { + .type = LANDLOCK_REQUEST_FS_ACCESS, + .audit = { + .type = LSM_AUDIT_DATA_IOCTL_OP, + .u.op = &(struct lsm_ioctlop_audit) { + .path = file->f_path, + .cmd = cmd, + }, + }, + .all_existing_optional_access = _LANDLOCK_ACCESS_FS_OPTIONAL, + .access = LANDLOCK_ACCESS_FS_IOCTL_DEV, +#ifdef CONFIG_AUDIT + .deny_masks = landlock_file(file)->deny_masks, +#endif /* CONFIG_AUDIT */ + }); return -EACCES; } +static int hook_file_ioctl(struct file *file, unsigned int cmd, + unsigned long arg) +{ + return hook_file_ioctl_common(file, cmd, false); +} + static int hook_file_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg) { - access_mask_t allowed_access = landlock_file(file)->allowed_access; + return hook_file_ioctl_common(file, cmd, true); +} + +/* + * Always allow sending signals between threads of the same process. This + * ensures consistency with hook_task_kill(). + */ +static bool control_current_fowner(struct fown_struct *const fown) +{ + struct task_struct *p; /* - * It is the access rights at the time of opening the file which - * determine whether IOCTL can be used on the opened file later. - * - * The access right is attached to the opened file in hook_file_open(). + * Lock already held by __f_setown(), see commit 26f204380a3c ("fs: Fix + * file_set_fowner LSM hook inconsistencies"). */ - if (allowed_access & LANDLOCK_ACCESS_FS_IOCTL_DEV) - return 0; + lockdep_assert_held(&fown->lock); - if (!is_device(file)) - return 0; - - if (is_masked_device_ioctl_compat(cmd)) - return 0; + /* + * Some callers (e.g. fcntl_dirnotify) may not be in an RCU read-side + * critical section. + */ + guard(rcu)(); + p = pid_task(fown->pid, fown->pid_type); + if (!p) + return true; - return -EACCES; + return !same_thread_group(p, current); } static void hook_file_set_fowner(struct file *file) { - struct landlock_ruleset *new_dom, *prev_dom; + struct landlock_ruleset *prev_dom; + struct landlock_cred_security fown_subject = {}; + size_t fown_layer = 0; + + if (control_current_fowner(file_f_owner(file))) { + static const struct access_masks signal_scope = { + .scope = LANDLOCK_SCOPE_SIGNAL, + }; + const struct landlock_cred_security *new_subject = + landlock_get_applicable_subject( + current_cred(), signal_scope, &fown_layer); + if (new_subject) { + landlock_get_ruleset(new_subject->domain); + fown_subject = *new_subject; + } + } - /* - * Lock already held by __f_setown(), see commit 26f204380a3c ("fs: Fix - * file_set_fowner LSM hook inconsistencies"). - */ - lockdep_assert_held(&file_f_owner(file)->lock); - new_dom = landlock_get_current_domain(); - landlock_get_ruleset(new_dom); - prev_dom = landlock_file(file)->fown_domain; - landlock_file(file)->fown_domain = new_dom; + prev_dom = landlock_file(file)->fown_subject.domain; + landlock_file(file)->fown_subject = fown_subject; +#ifdef CONFIG_AUDIT + landlock_file(file)->fown_layer = fown_layer; +#endif /* CONFIG_AUDIT*/ - /* Called in an RCU read-side critical section. */ + /* May be called in an RCU read-side critical section. */ landlock_put_ruleset_deferred(prev_dom); } static void hook_file_free_security(struct file *file) { - landlock_put_ruleset_deferred(landlock_file(file)->fown_domain); + landlock_put_ruleset_deferred(landlock_file(file)->fown_subject.domain); } static struct security_hook_list landlock_hooks[] __ro_after_init = { |