Add audit support for sb_mount, move_mount, sb_umount, sb_remount, and sb_pivot_root hooks.
The new related blocker is "fs.change_layout". Add and use a new landlock_match_layer_level() helper. Audit event sample: type=LANDLOCK_DENY msg=audit(1729738800.349:44): domain=195ba459b blockers=fs.change_layout name="/" dev="tmpfs" ino=1 Cc: Günther Noack <[email protected]> Signed-off-by: Mickaël Salaün <[email protected]> Link: https://lore.kernel.org/r/[email protected] --- Changes since v3: - Cosmetic change to the "fs.change_layout" name. Changes since v2: - Log the domain that denied the action because not all layers block FS layout changes. - Fix landlock_match_layer_level(). Changes since v1: - Rebased on the TCP patch series. - Don't log missing permissions, only domain layer, and then remove the permission word (suggested by Günther) --- security/landlock/audit.c | 3 ++ security/landlock/audit.h | 1 + security/landlock/fs.c | 64 ++++++++++++++++++++++++++++++++++--- security/landlock/ruleset.h | 31 ++++++++++++++++++ 4 files changed, 94 insertions(+), 5 deletions(-) diff --git a/security/landlock/audit.c b/security/landlock/audit.c index ccc591146f8a..aae93b2c994b 100644 --- a/security/landlock/audit.c +++ b/security/landlock/audit.c @@ -20,6 +20,9 @@ static const char *get_blocker(const enum landlock_request_type type) switch (type) { case LANDLOCK_REQUEST_PTRACE: return "ptrace"; + + case LANDLOCK_REQUEST_FS_CHANGE_LAYOUT: + return "fs.change_layout"; } WARN_ON_ONCE(1); diff --git a/security/landlock/audit.h b/security/landlock/audit.h index 7bc67ca2e470..745dcf7b1b6d 100644 --- a/security/landlock/audit.h +++ b/security/landlock/audit.h @@ -15,6 +15,7 @@ enum landlock_request_type { LANDLOCK_REQUEST_PTRACE = 1, + LANDLOCK_REQUEST_FS_CHANGE_LAYOUT, }; /* diff --git a/security/landlock/fs.c b/security/landlock/fs.c index 9779170d9199..171012efb559 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -23,6 +23,7 @@ #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> @@ -37,6 +38,7 @@ #include <uapi/linux/landlock.h> #include "access.h" +#include "audit.h" #include "common.h" #include "cred.h" #include "fs.h" @@ -1301,6 +1303,38 @@ static void hook_sb_delete(struct super_block *const sb) !atomic_long_read(&landlock_superblock(sb)->inode_refs)); } +static void +log_fs_change_layout_path(const struct landlock_ruleset *const domain, + const struct path *const path) +{ + const struct landlock_request request = { + .type = LANDLOCK_REQUEST_FS_CHANGE_LAYOUT, + .audit = { + .type = LSM_AUDIT_DATA_PATH, + .u.path = *path, + }, + .layer_plus_one = landlock_match_layer_level(domain, any_fs) + 1, + }; + + landlock_log_denial(domain, &request); +} + +static void +log_fs_change_layout_dentry(const struct landlock_ruleset *const domain, + struct dentry *const dentry) +{ + const struct landlock_request request = { + .type = LANDLOCK_REQUEST_FS_CHANGE_LAYOUT, + .audit = { + .type = LSM_AUDIT_DATA_DENTRY, + .u.dentry = dentry, + }, + .layer_plus_one = landlock_match_layer_level(domain, any_fs) + 1, + }; + + landlock_log_denial(domain, &request); +} + /* * Because a Landlock security policy is defined according to the filesystem * topology (i.e. the mount namespace), changing it may grant access to files @@ -1323,16 +1357,24 @@ 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()) + const struct landlock_ruleset *const dom = get_current_fs_domain(); + + if (!dom) return 0; + + log_fs_change_layout_path(dom, 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()) + const struct landlock_ruleset *const dom = get_current_fs_domain(); + + if (!dom) return 0; + + log_fs_change_layout_path(dom, to_path); return -EPERM; } @@ -1342,15 +1384,23 @@ 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()) + const struct landlock_ruleset *const dom = get_current_fs_domain(); + + if (!dom) return 0; + + log_fs_change_layout_dentry(dom, mnt->mnt_root); return -EPERM; } static int hook_sb_remount(struct super_block *const sb, void *const mnt_opts) { - if (!get_current_fs_domain()) + const struct landlock_ruleset *const dom = get_current_fs_domain(); + + if (!dom) return 0; + + log_fs_change_layout_dentry(dom, sb->s_root); return -EPERM; } @@ -1365,8 +1415,12 @@ 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()) + const struct landlock_ruleset *const dom = get_current_fs_domain(); + + if (!dom) return 0; + + log_fs_change_layout_path(dom, new_path); return -EPERM; } diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h index 39169b6860e3..7dba8bf960f6 100644 --- a/security/landlock/ruleset.h +++ b/security/landlock/ruleset.h @@ -267,6 +267,37 @@ landlock_get_applicable_domain(const struct landlock_ruleset *const domain, return NULL; } +/** + * landlock_match_layer_level - Return the layer level restricting @masks + * + * @domain: Landlock ruleset (used as a domain) + * @masks: access masks + * + * Returns: the number of the layer restricting/handling any right of @access, + * or return 0 (i.e. first layer) otherwise. + */ +static inline size_t +landlock_match_layer_level(const struct landlock_ruleset *const domain, + const struct access_masks masks) +{ + const union access_masks_all masks_all = { + .masks = masks, + }; + ssize_t layer_level; + + for (layer_level = domain->num_layers; layer_level >= 0; + layer_level--) { + union access_masks_all layer = { + .masks = domain->access_masks[layer_level], + }; + + if (masks_all.all & layer.all) + return layer_level; + } + + return 0; +} + static inline void landlock_add_fs_access_mask(struct landlock_ruleset *const ruleset, const access_mask_t fs_access_mask, -- 2.47.1
