From 0c0effb07f7d662af3e6f74da4d34241e412029b Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= Date: Sat, 9 Nov 2024 12:08:54 +0100 Subject: [PATCH] landlock: Refactor filesystem access mask management MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Replace get_raw_handled_fs_accesses() with a generic landlock_union_access_masks(), and replace get_fs_domain() with a generic landlock_get_applicable_domain(). These helpers will also be useful for other types of access. Cc: Mikhail Ivanov Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20241109110856.222842-2-mic@digikod.net [mic: Slightly improve doc as suggested by Günther] Signed-off-by: Mickaël Salaün --- security/landlock/fs.c | 31 ++++----------- security/landlock/ruleset.h | 74 ++++++++++++++++++++++++++++++++---- security/landlock/syscalls.c | 2 +- 3 files changed, 75 insertions(+), 32 deletions(-) diff --git a/security/landlock/fs.c b/security/landlock/fs.c index 7d79fc8abe21..e31b97a9f175 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -388,38 +388,22 @@ static bool is_nouser_or_private(const struct dentry *dentry) unlikely(IS_PRIVATE(d_backing_inode(dentry)))); } -static access_mask_t -get_raw_handled_fs_accesses(const struct landlock_ruleset *const domain) -{ - access_mask_t access_dom = 0; - size_t layer_level; - - for (layer_level = 0; layer_level < domain->num_layers; layer_level++) - access_dom |= - landlock_get_raw_fs_access_mask(domain, layer_level); - return access_dom; -} - static access_mask_t get_handled_fs_accesses(const struct landlock_ruleset *const domain) { /* Handles all initially denied by default access rights. */ - return get_raw_handled_fs_accesses(domain) | + return landlock_union_access_masks(domain).fs | LANDLOCK_ACCESS_FS_INITIALLY_DENIED; } -static const struct landlock_ruleset * -get_fs_domain(const struct landlock_ruleset *const domain) -{ - if (!domain || !get_raw_handled_fs_accesses(domain)) - return NULL; - - return domain; -} +static const struct access_masks any_fs = { + .fs = ~0, +}; static const struct landlock_ruleset *get_current_fs_domain(void) { - return get_fs_domain(landlock_get_current_domain()); + return landlock_get_applicable_domain(landlock_get_current_domain(), + any_fs); } /* @@ -1517,7 +1501,8 @@ static int hook_file_open(struct file *const file) access_mask_t open_access_request, full_access_request, allowed_access, optional_access; const struct landlock_ruleset *const dom = - get_fs_domain(landlock_cred(file->f_cred)->domain); + landlock_get_applicable_domain( + landlock_cred(file->f_cred)->domain, any_fs); if (!dom) return 0; diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h index 61bdbc550172..631e24d4ffe9 100644 --- a/security/landlock/ruleset.h +++ b/security/landlock/ruleset.h @@ -11,6 +11,7 @@ #include #include +#include #include #include #include @@ -47,6 +48,15 @@ struct access_masks { access_mask_t scope : LANDLOCK_NUM_SCOPE; }; +union access_masks_all { + struct access_masks masks; + u32 all; +}; + +/* Makes sure all fields are covered. */ +static_assert(sizeof(typeof_member(union access_masks_all, masks)) == + sizeof(typeof_member(union access_masks_all, all))); + typedef u16 layer_mask_t; /* Makes sure all layers can be checked. */ static_assert(BITS_PER_TYPE(layer_mask_t) >= LANDLOCK_MAX_NUM_LAYERS); @@ -260,6 +270,61 @@ static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset) refcount_inc(&ruleset->usage); } +/** + * landlock_union_access_masks - Return all access rights handled in the + * domain + * + * @domain: Landlock ruleset (used as a domain) + * + * Returns: an access_masks result of the OR of all the domain's access masks. + */ +static inline struct access_masks +landlock_union_access_masks(const struct landlock_ruleset *const domain) +{ + union access_masks_all matches = {}; + size_t layer_level; + + for (layer_level = 0; layer_level < domain->num_layers; layer_level++) { + union access_masks_all layer = { + .masks = domain->access_masks[layer_level], + }; + + matches.all |= layer.all; + } + + return matches.masks; +} + +/** + * landlock_get_applicable_domain - Return @domain if it applies to (handles) + * at least one of the access rights specified + * in @masks + * + * @domain: Landlock ruleset (used as a domain) + * @masks: access masks + * + * Returns: @domain if any access rights specified in @masks is handled, or + * NULL otherwise. + */ +static inline const struct landlock_ruleset * +landlock_get_applicable_domain(const struct landlock_ruleset *const domain, + const struct access_masks masks) +{ + const union access_masks_all masks_all = { + .masks = masks, + }; + union access_masks_all merge = {}; + + if (!domain) + return NULL; + + merge.masks = landlock_union_access_masks(domain); + if (merge.all & masks_all.all) + return domain; + + return NULL; +} + static inline void landlock_add_fs_access_mask(struct landlock_ruleset *const ruleset, const access_mask_t fs_access_mask, @@ -295,19 +360,12 @@ landlock_add_scope_mask(struct landlock_ruleset *const ruleset, ruleset->access_masks[layer_level].scope |= mask; } -static inline access_mask_t -landlock_get_raw_fs_access_mask(const struct landlock_ruleset *const ruleset, - const u16 layer_level) -{ - return ruleset->access_masks[layer_level].fs; -} - static inline access_mask_t landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset, const u16 layer_level) { /* Handles all initially denied by default access rights. */ - return landlock_get_raw_fs_access_mask(ruleset, layer_level) | + return ruleset->access_masks[layer_level].fs | LANDLOCK_ACCESS_FS_INITIALLY_DENIED; } diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c index f5a0e7182ec0..c097d356fa45 100644 --- a/security/landlock/syscalls.c +++ b/security/landlock/syscalls.c @@ -329,7 +329,7 @@ static int add_rule_path_beneath(struct landlock_ruleset *const ruleset, return -ENOMSG; /* Checks that allowed_access matches the @ruleset constraints. */ - mask = landlock_get_raw_fs_access_mask(ruleset, 0); + mask = ruleset->access_masks[0].fs; if ((path_beneath_attr.allowed_access | mask) != mask) return -EINVAL;