From patchwork Mon May 16 15:20:27 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Konstantin Meskhidze (A)" X-Patchwork-Id: 12850950 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 98047C433EF for ; Mon, 16 May 2022 15:21:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245207AbiEPPVZ (ORCPT ); Mon, 16 May 2022 11:21:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58084 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245194AbiEPPVD (ORCPT ); Mon, 16 May 2022 11:21:03 -0400 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9F0CE3B3F1; Mon, 16 May 2022 08:20:54 -0700 (PDT) Received: from fraeml704-chm.china.huawei.com (unknown [172.18.147.226]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4L22y94yGFz67XGR; Mon, 16 May 2022 23:20:49 +0800 (CST) Received: from mscphispre00059.huawei.com (10.123.71.64) by fraeml704-chm.china.huawei.com (10.206.15.53) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2375.24; Mon, 16 May 2022 17:20:52 +0200 From: Konstantin Meskhidze To: CC: , , , , , Subject: [PATCH v5 04/15] landlock: helper functions refactoring Date: Mon, 16 May 2022 23:20:27 +0800 Message-ID: <20220516152038.39594-5-konstantin.meskhidze@huawei.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220516152038.39594-1-konstantin.meskhidze@huawei.com> References: <20220516152038.39594-1-konstantin.meskhidze@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.123.71.64] X-ClientProxiedBy: mscpeml500001.china.huawei.com (7.188.26.142) To fraeml704-chm.china.huawei.com (10.206.15.53) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Unmask_layers(), init_layer_masks() and get_handled_accesses() helper functions move to ruleset.c and rule_type argument is added. This modification supports implementing new rule types into next landlock versions. Signed-off-by: Konstantin Meskhidze --- Changes since v3: * Splits commit. * Refactoring landlock_unmask_layers functions. Changes since v4: * Refactoring init_layer_masks(), get_handled_accesses() and unmask_layers() functions to support multiple rule types. * Refactoring landlock_get_fs_access_mask() function with LANDLOCK_MASK_ACCESS_FS mask. --- security/landlock/fs.c | 158 ++++++++---------------------------- security/landlock/ruleset.c | 152 +++++++++++++++++++++++++++++++--- security/landlock/ruleset.h | 17 +++- 3 files changed, 192 insertions(+), 135 deletions(-) -- 2.25.1 diff --git a/security/landlock/fs.c b/security/landlock/fs.c index 5de24d4dd74c..3506e182b23e 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -211,60 +211,6 @@ find_rule(const struct landlock_ruleset *const domain, return rule; } -/* - * @layer_masks is read and may be updated according to the access request and - * the matching rule. - * - * Returns true if the request is allowed (i.e. relevant layer masks for the - * request are empty). - */ -static inline bool -unmask_layers(const struct landlock_rule *const rule, - const access_mask_t access_request, - layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS]) -{ - size_t layer_level; - - if (!access_request || !layer_masks) - return true; - if (!rule) - return false; - - /* - * An access is granted if, for each policy layer, at least one rule - * encountered on the pathwalk grants the requested access, - * regardless of its position in the layer stack. We must then check - * the remaining layers for each inode, from the first added layer to - * the last one. When there is multiple requested accesses, for each - * policy layer, the full set of requested accesses may not be granted - * by only one rule, but by the union (binary OR) of multiple rules. - * E.g. /a/b + /a => /a/b - */ - for (layer_level = 0; layer_level < rule->num_layers; layer_level++) { - const struct landlock_layer *const layer = - &rule->layers[layer_level]; - const layer_mask_t layer_bit = BIT_ULL(layer->level - 1); - const unsigned long access_req = access_request; - unsigned long access_bit; - bool is_empty; - - /* - * Records in @layer_masks which layer grants access to each - * requested access. - */ - is_empty = true; - for_each_set_bit(access_bit, &access_req, - ARRAY_SIZE(*layer_masks)) { - if (layer->access & BIT_ULL(access_bit)) - (*layer_masks)[access_bit] &= ~layer_bit; - is_empty = is_empty && !(*layer_masks)[access_bit]; - } - if (is_empty) - return true; - } - return false; -} - /* * Allows access to pseudo filesystems that will never be mountable (e.g. * sockfs, pipefs), but can still be reachable through @@ -277,59 +223,6 @@ static inline bool is_nouser_or_private(const struct dentry *dentry) unlikely(IS_PRIVATE(d_backing_inode(dentry)))); } -static inline access_mask_t -get_handled_accesses(const struct landlock_ruleset *const domain) -{ - access_mask_t access_dom = 0; - unsigned long access_bit; - - for (access_bit = 0; access_bit < LANDLOCK_NUM_ACCESS_FS; - access_bit++) { - size_t layer_level; - - for (layer_level = 0; layer_level < domain->num_layers; - layer_level++) { - if (landlock_get_fs_access_mask(domain, layer_level) & - BIT_ULL(access_bit)) { - access_dom |= BIT_ULL(access_bit); - break; - } - } - } - return access_dom; -} - -static inline access_mask_t -init_layer_masks(const struct landlock_ruleset *const domain, - const access_mask_t access_request, - layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS]) -{ - access_mask_t handled_accesses = 0; - size_t layer_level; - - memset(layer_masks, 0, sizeof(*layer_masks)); - /* An empty access request can happen because of O_WRONLY | O_RDWR. */ - if (!access_request) - return 0; - - /* Saves all handled accesses per layer. */ - for (layer_level = 0; layer_level < domain->num_layers; layer_level++) { - const unsigned long access_req = access_request; - unsigned long access_bit; - - for_each_set_bit(access_bit, &access_req, - ARRAY_SIZE(*layer_masks)) { - if (landlock_get_fs_access_mask(domain, layer_level) & - BIT_ULL(access_bit)) { - (*layer_masks)[access_bit] |= - BIT_ULL(layer_level); - handled_accesses |= BIT_ULL(access_bit); - } - } - } - return handled_accesses; -} - /* * Check that a destination file hierarchy has more restrictions than a source * file hierarchy. This is only used for link and rename actions. @@ -506,7 +399,8 @@ static int check_access_path_dual( * a superset of the meaningful requested accesses). */ access_masked_parent1 = access_masked_parent2 = - get_handled_accesses(domain); + get_handled_accesses(domain, LANDLOCK_RULE_PATH_BENEATH, + LANDLOCK_NUM_ACCESS_FS); is_dom_check = true; } else { if (WARN_ON_ONCE(dentry_child1 || dentry_child2)) @@ -519,17 +413,25 @@ static int check_access_path_dual( if (unlikely(dentry_child1)) { unmask_layers(find_rule(domain, dentry_child1), - init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS, - &_layer_masks_child1), - &_layer_masks_child1); + init_layer_masks(domain, + LANDLOCK_MASK_ACCESS_FS, + &_layer_masks_child1, + sizeof(_layer_masks_child1), + LANDLOCK_RULE_PATH_BENEATH), + &_layer_masks_child1, + ARRAY_SIZE(_layer_masks_child1)); layer_masks_child1 = &_layer_masks_child1; child1_is_directory = d_is_dir(dentry_child1); } if (unlikely(dentry_child2)) { unmask_layers(find_rule(domain, dentry_child2), - init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS, - &_layer_masks_child2), - &_layer_masks_child2); + init_layer_masks(domain, + LANDLOCK_MASK_ACCESS_FS, + &_layer_masks_child2, + sizeof(_layer_masks_child2), + LANDLOCK_RULE_PATH_BENEATH), + &_layer_masks_child2, + ARRAY_SIZE(_layer_masks_child2)); layer_masks_child2 = &_layer_masks_child2; child2_is_directory = d_is_dir(dentry_child2); } @@ -582,14 +484,15 @@ static int check_access_path_dual( rule = find_rule(domain, walker_path.dentry); allowed_parent1 = unmask_layers(rule, access_masked_parent1, - layer_masks_parent1); + layer_masks_parent1, + ARRAY_SIZE(*layer_masks_parent1)); allowed_parent2 = unmask_layers(rule, access_masked_parent2, - layer_masks_parent2); + layer_masks_parent2, + ARRAY_SIZE(*layer_masks_parent2)); /* Stops when a rule from each layer grants access. */ if (allowed_parent1 && allowed_parent2) break; - jump_up: if (walker_path.dentry == walker_path.mnt->mnt_root) { if (follow_up(&walker_path)) { @@ -645,7 +548,9 @@ static inline int check_access_path(const struct landlock_ruleset *const domain, { layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {}; - access_request = init_layer_masks(domain, access_request, &layer_masks); + access_request = init_layer_masks(domain, access_request, + &layer_masks, sizeof(layer_masks), + LANDLOCK_RULE_PATH_BENEATH); return check_access_path_dual(domain, path, access_request, &layer_masks, NULL, 0, NULL, NULL); } @@ -729,7 +634,8 @@ static bool collect_domain_accesses( return true; access_dom = init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS, - layer_masks_dom); + layer_masks_dom, sizeof(*layer_masks_dom), + LANDLOCK_RULE_PATH_BENEATH); dget(dir); while (true) { @@ -737,7 +643,8 @@ static bool collect_domain_accesses( /* Gets all layers allowing all domain accesses. */ if (unmask_layers(find_rule(domain, dir), access_dom, - layer_masks_dom)) { + layer_masks_dom, + ARRAY_SIZE(*layer_masks_dom))) { /* * Stops when all handled accesses are allowed by at * least one rule in each layer. @@ -851,9 +758,10 @@ static int current_check_refer_path(struct dentry *const old_dentry, * The LANDLOCK_ACCESS_FS_REFER access right is not required * for same-directory referer (i.e. no reparenting). */ - access_request_parent1 = init_layer_masks( - dom, access_request_parent1 | access_request_parent2, - &layer_masks_parent1); + access_request_parent1 = init_layer_masks(dom, + access_request_parent1 | access_request_parent2, + &layer_masks_parent1, sizeof(layer_masks_parent1), + LANDLOCK_RULE_PATH_BENEATH); return check_access_path_dual(dom, new_dir, access_request_parent1, &layer_masks_parent1, NULL, 0, @@ -861,7 +769,9 @@ static int current_check_refer_path(struct dentry *const old_dentry, } /* Backward compatibility: no reparenting support. */ - if (!(get_handled_accesses(dom) & LANDLOCK_ACCESS_FS_REFER)) + if (!(get_handled_accesses(dom, LANDLOCK_RULE_PATH_BENEATH, + LANDLOCK_NUM_ACCESS_FS) & + LANDLOCK_ACCESS_FS_REFER)) return -EXDEV; access_request_parent1 |= LANDLOCK_ACCESS_FS_REFER; diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c index 4b4c9953bb32..c4ed783d655b 100644 --- a/security/landlock/ruleset.c +++ b/security/landlock/ruleset.c @@ -233,7 +233,8 @@ static int insert_rule(struct landlock_ruleset *const ruleset, &(*layers)[0]); if (IS_ERR(new_rule)) return PTR_ERR(new_rule); - rb_replace_node(&this->node, &new_rule->node, &ruleset->root_inode); + rb_replace_node(&this->node, &new_rule->node, + &ruleset->root_inode); free_rule(this, rule_type); break; } @@ -246,7 +247,8 @@ static int insert_rule(struct landlock_ruleset *const ruleset, return -E2BIG; switch (rule_type) { case LANDLOCK_RULE_PATH_BENEATH: - new_rule = create_rule(object_ptr, 0, layers, num_layers, NULL); + new_rule = create_rule(object_ptr, 0, layers, + num_layers, NULL); if (IS_ERR(new_rule)) return PTR_ERR(new_rule); rb_link_node(&new_rule->node, parent_node, walker_node); @@ -281,8 +283,8 @@ int landlock_insert_rule(struct landlock_ruleset *const ruleset, } }; build_check_layer(); - return insert_rule(ruleset, object_ptr, object_data, rule_type, &layers, - ARRAY_SIZE(layers)); + return insert_rule(ruleset, object_ptr, object_data, rule_type, + &layers, ARRAY_SIZE(layers)); } static inline void get_hierarchy(struct landlock_hierarchy *const hierarchy) @@ -335,8 +337,9 @@ static int tree_merge(struct landlock_ruleset *const src, switch (rule_type) { case LANDLOCK_RULE_PATH_BENEATH: - err = insert_rule(dst, walker_rule->object.ptr, 0, rule_type, - &layers, ARRAY_SIZE(layers)); + err = insert_rule(dst, walker_rule->object.ptr, 0, + rule_type, &layers, + ARRAY_SIZE(layers)); break; } if (err) @@ -433,9 +436,13 @@ static int inherit_ruleset(struct landlock_ruleset *const parent, err = -EINVAL; goto out_unlock; } - /* Copies the parent layer stack and leaves a space for the new layer. */ + /* + * Copies the parent layer stack and leaves a space + * for the new layer. + */ memcpy(child->access_masks, parent->access_masks, - flex_array_size(parent, access_masks, parent->num_layers)); + flex_array_size(parent, access_masks, + parent->num_layers)); if (WARN_ON_ONCE(!parent->hierarchy)) { err = -EINVAL; @@ -455,8 +462,9 @@ static void free_ruleset(struct landlock_ruleset *const ruleset) struct landlock_rule *freeme, *next; might_sleep(); - rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root_inode, - node) + rbtree_postorder_for_each_entry_safe(freeme, next, + &ruleset->root_inode, + node) free_rule(freeme, LANDLOCK_RULE_PATH_BENEATH); put_hierarchy(ruleset->hierarchy); kfree(ruleset); @@ -577,3 +585,127 @@ const struct landlock_rule *landlock_find_rule( } return NULL; } + +access_mask_t get_handled_accesses( + const struct landlock_ruleset *const domain, + u16 rule_type, u16 num_access) +{ + access_mask_t access_dom = 0; + unsigned long access_bit; + + switch (rule_type) { + case LANDLOCK_RULE_PATH_BENEATH: + for (access_bit = 0; access_bit < LANDLOCK_NUM_ACCESS_FS; + access_bit++) { + size_t layer_level; + + for (layer_level = 0; layer_level < domain->num_layers; + layer_level++) { + if (landlock_get_fs_access_mask(domain, + layer_level) & + BIT_ULL(access_bit)) { + access_dom |= BIT_ULL(access_bit); + break; + } + } + } + break; + default: + break; + } + return access_dom; +} + +/* + * @layer_masks is read and may be updated according to the access request and + * the matching rule. + * + * Returns true if the request is allowed (i.e. relevant layer masks for the + * request are empty). + */ +bool unmask_layers(const struct landlock_rule *const rule, + const access_mask_t access_request, + layer_mask_t (*const layer_masks)[], size_t masks_array_size) +{ + size_t layer_level; + + if (!access_request || !layer_masks) + return true; + if (!rule) + return false; + + /* + * An access is granted if, for each policy layer, at least one rule + * encountered on the pathwalk grants the requested access, + * regardless of its position in the layer stack. We must then check + * the remaining layers for each inode, from the first added layer to + * the last one. When there is multiple requested accesses, for each + * policy layer, the full set of requested accesses may not be granted + * by only one rule, but by the union (binary OR) of multiple rules. + * E.g. /a/b + /a => /a/b + */ + for (layer_level = 0; layer_level < rule->num_layers; layer_level++) { + const struct landlock_layer *const layer = + &rule->layers[layer_level]; + const layer_mask_t layer_bit = BIT_ULL(layer->level - 1); + const unsigned long access_req = access_request; + unsigned long access_bit; + bool is_empty; + + /* + * Records in @layer_masks which layer grants access to each + * requested access. + */ + is_empty = true; + for_each_set_bit(access_bit, &access_req, masks_array_size) { + if (layer->access & BIT_ULL(access_bit)) + (*layer_masks)[access_bit] &= ~layer_bit; + is_empty = is_empty && !(*layer_masks)[access_bit]; + } + if (is_empty) + return true; + } + return false; +} + +access_mask_t init_layer_masks(const struct landlock_ruleset *const domain, + const access_mask_t access_request, + layer_mask_t (*const layer_masks)[], + size_t masks_size, + u16 rule_type) +{ + access_mask_t handled_accesses = 0; + size_t layer_level; + + memset(layer_masks, 0, masks_size); + + /* An empty access request can happen because of O_WRONLY | O_RDWR. */ + if (!access_request) + return 0; + + /* Saves all handled accesses per layer. */ + for (layer_level = 0; layer_level < domain->num_layers; + layer_level++) { + const unsigned long access_req = access_request; + unsigned long access_bit; + + switch (rule_type) { + case LANDLOCK_RULE_PATH_BENEATH: + for_each_set_bit(access_bit, &access_req, + LANDLOCK_NUM_ACCESS_FS) { + if (landlock_get_fs_access_mask(domain, + layer_level) & + BIT_ULL(access_bit)) { + (*layer_masks)[access_bit] |= + BIT_ULL(layer_level); + handled_accesses |= + BIT_ULL(access_bit); + } + } + break; + default: + return 0; + } + } + return handled_accesses; +} diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h index 3066e5d7180c..f3cd890d0348 100644 --- a/security/landlock/ruleset.h +++ b/security/landlock/ruleset.h @@ -195,7 +195,22 @@ static inline u32 landlock_get_fs_access_mask( const struct landlock_ruleset *ruleset, u16 mask_level) { - return ruleset->access_masks[mask_level]; + return (ruleset->access_masks[mask_level] & LANDLOCK_MASK_ACCESS_FS); } +access_mask_t get_handled_accesses( + const struct landlock_ruleset *const domain, + u16 rule_type, u16 num_access); + +bool unmask_layers(const struct landlock_rule *const rule, + const access_mask_t access_request, + layer_mask_t (*const layer_masks)[], + size_t masks_array_size); + +access_mask_t init_layer_masks(const struct landlock_ruleset *const domain, + const access_mask_t access_request, + layer_mask_t (*const layer_masks)[], + size_t masks_size, + u16 rule_type); + #endif /* _SECURITY_LANDLOCK_RULESET_H */