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landlock: Move and rename layer helpers
Move and rename landlock_unmask_layers() and landlock_init_layer_masks() helpers to ruleset.c to share them with Landlock network implementation in following commits. Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com> Link: https://lore.kernel.org/r/20231026014751.414649-6-konstantin.meskhidze@huawei.com Signed-off-by: Mickaël Salaün <mic@digikod.net>
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@ -215,60 +215,6 @@ find_rule(const struct landlock_ruleset *const domain,
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return rule;
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}
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/*
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* @layer_masks is read and may be updated according to the access request and
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* the matching rule.
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*
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* Returns true if the request is allowed (i.e. relevant layer masks for the
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* request are empty).
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*/
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static inline bool
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unmask_layers(const struct landlock_rule *const rule,
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const access_mask_t access_request,
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layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
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{
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size_t layer_level;
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if (!access_request || !layer_masks)
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return true;
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if (!rule)
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return false;
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/*
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* An access is granted if, for each policy layer, at least one rule
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* encountered on the pathwalk grants the requested access,
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* regardless of its position in the layer stack. We must then check
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* the remaining layers for each inode, from the first added layer to
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* the last one. When there is multiple requested accesses, for each
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* policy layer, the full set of requested accesses may not be granted
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* by only one rule, but by the union (binary OR) of multiple rules.
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* E.g. /a/b <execute> + /a <read> => /a/b <execute + read>
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*/
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for (layer_level = 0; layer_level < rule->num_layers; layer_level++) {
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const struct landlock_layer *const layer =
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&rule->layers[layer_level];
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const layer_mask_t layer_bit = BIT_ULL(layer->level - 1);
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const unsigned long access_req = access_request;
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unsigned long access_bit;
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bool is_empty;
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/*
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* Records in @layer_masks which layer grants access to each
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* requested access.
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*/
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is_empty = true;
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for_each_set_bit(access_bit, &access_req,
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ARRAY_SIZE(*layer_masks)) {
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if (layer->access & BIT_ULL(access_bit))
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(*layer_masks)[access_bit] &= ~layer_bit;
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is_empty = is_empty && !(*layer_masks)[access_bit];
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}
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if (is_empty)
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return true;
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}
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return false;
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}
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/*
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* Allows access to pseudo filesystems that will never be mountable (e.g.
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* sockfs, pipefs), but can still be reachable through
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@ -293,50 +239,6 @@ get_raw_handled_fs_accesses(const struct landlock_ruleset *const domain)
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return access_dom;
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}
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/**
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* init_layer_masks - Initialize layer masks from an access request
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*
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* Populates @layer_masks such that for each access right in @access_request,
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* the bits for all the layers are set where this access right is handled.
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*
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* @domain: The domain that defines the current restrictions.
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* @access_request: The requested access rights to check.
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* @layer_masks: The layer masks to populate.
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*
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* Returns: An access mask where each access right bit is set which is handled
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* in any of the active layers in @domain.
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*/
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static inline access_mask_t
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init_layer_masks(const struct landlock_ruleset *const domain,
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const access_mask_t access_request,
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layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
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{
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access_mask_t handled_accesses = 0;
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size_t layer_level;
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memset(layer_masks, 0, sizeof(*layer_masks));
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/* An empty access request can happen because of O_WRONLY | O_RDWR. */
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if (!access_request)
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return 0;
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/* Saves all handled accesses per layer. */
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for (layer_level = 0; layer_level < domain->num_layers; layer_level++) {
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const unsigned long access_req = access_request;
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unsigned long access_bit;
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for_each_set_bit(access_bit, &access_req,
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ARRAY_SIZE(*layer_masks)) {
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if (BIT_ULL(access_bit) &
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landlock_get_fs_access_mask(domain, layer_level)) {
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(*layer_masks)[access_bit] |=
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BIT_ULL(layer_level);
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handled_accesses |= BIT_ULL(access_bit);
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}
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}
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}
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return handled_accesses;
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}
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static access_mask_t
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get_handled_fs_accesses(const struct landlock_ruleset *const domain)
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{
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@ -540,18 +442,20 @@ static bool is_access_to_paths_allowed(
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}
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if (unlikely(dentry_child1)) {
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unmask_layers(find_rule(domain, dentry_child1),
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init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
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landlock_unmask_layers(find_rule(domain, dentry_child1),
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landlock_init_layer_masks(
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domain, LANDLOCK_MASK_ACCESS_FS,
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&_layer_masks_child1),
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&_layer_masks_child1);
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&_layer_masks_child1);
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layer_masks_child1 = &_layer_masks_child1;
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child1_is_directory = d_is_dir(dentry_child1);
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}
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if (unlikely(dentry_child2)) {
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unmask_layers(find_rule(domain, dentry_child2),
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init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
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landlock_unmask_layers(find_rule(domain, dentry_child2),
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landlock_init_layer_masks(
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domain, LANDLOCK_MASK_ACCESS_FS,
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&_layer_masks_child2),
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&_layer_masks_child2);
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&_layer_masks_child2);
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layer_masks_child2 = &_layer_masks_child2;
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child2_is_directory = d_is_dir(dentry_child2);
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}
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@ -603,10 +507,10 @@ static bool is_access_to_paths_allowed(
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}
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rule = find_rule(domain, walker_path.dentry);
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allowed_parent1 = unmask_layers(rule, access_masked_parent1,
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layer_masks_parent1);
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allowed_parent2 = unmask_layers(rule, access_masked_parent2,
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layer_masks_parent2);
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allowed_parent1 = landlock_unmask_layers(
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rule, access_masked_parent1, layer_masks_parent1);
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allowed_parent2 = landlock_unmask_layers(
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rule, access_masked_parent2, layer_masks_parent2);
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/* Stops when a rule from each layer grants access. */
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if (allowed_parent1 && allowed_parent2)
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@ -650,7 +554,8 @@ static inline int check_access_path(const struct landlock_ruleset *const domain,
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{
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layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {};
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access_request = init_layer_masks(domain, access_request, &layer_masks);
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access_request =
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landlock_init_layer_masks(domain, access_request, &layer_masks);
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if (is_access_to_paths_allowed(domain, path, access_request,
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&layer_masks, NULL, 0, NULL, NULL))
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return 0;
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@ -735,16 +640,16 @@ static bool collect_domain_accesses(
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if (is_nouser_or_private(dir))
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return true;
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access_dom = init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
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layer_masks_dom);
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access_dom = landlock_init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
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layer_masks_dom);
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dget(dir);
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while (true) {
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struct dentry *parent_dentry;
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/* Gets all layers allowing all domain accesses. */
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if (unmask_layers(find_rule(domain, dir), access_dom,
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layer_masks_dom)) {
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if (landlock_unmask_layers(find_rule(domain, dir), access_dom,
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layer_masks_dom)) {
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/*
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* Stops when all handled accesses are allowed by at
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* least one rule in each layer.
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@ -857,7 +762,7 @@ static int current_check_refer_path(struct dentry *const old_dentry,
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* The LANDLOCK_ACCESS_FS_REFER access right is not required
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* for same-directory referer (i.e. no reparenting).
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*/
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access_request_parent1 = init_layer_masks(
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access_request_parent1 = landlock_init_layer_masks(
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dom, access_request_parent1 | access_request_parent2,
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&layer_masks_parent1);
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if (is_access_to_paths_allowed(
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@ -1234,7 +1139,8 @@ static int hook_file_open(struct file *const file)
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if (is_access_to_paths_allowed(
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dom, &file->f_path,
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init_layer_masks(dom, full_access_request, &layer_masks),
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landlock_init_layer_masks(dom, full_access_request,
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&layer_masks),
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&layer_masks, NULL, 0, NULL, NULL)) {
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allowed_access = full_access_request;
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} else {
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@ -569,3 +569,101 @@ landlock_find_rule(const struct landlock_ruleset *const ruleset,
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}
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return NULL;
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}
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/*
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* @layer_masks is read and may be updated according to the access request and
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* the matching rule.
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*
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* Returns true if the request is allowed (i.e. relevant layer masks for the
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* request are empty).
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*/
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bool landlock_unmask_layers(
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const struct landlock_rule *const rule,
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const access_mask_t access_request,
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layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
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{
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size_t layer_level;
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if (!access_request || !layer_masks)
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return true;
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if (!rule)
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return false;
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/*
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* An access is granted if, for each policy layer, at least one rule
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* encountered on the pathwalk grants the requested access,
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* regardless of its position in the layer stack. We must then check
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* the remaining layers for each inode, from the first added layer to
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* the last one. When there is multiple requested accesses, for each
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* policy layer, the full set of requested accesses may not be granted
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* by only one rule, but by the union (binary OR) of multiple rules.
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* E.g. /a/b <execute> + /a <read> => /a/b <execute + read>
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*/
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for (layer_level = 0; layer_level < rule->num_layers; layer_level++) {
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const struct landlock_layer *const layer =
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&rule->layers[layer_level];
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const layer_mask_t layer_bit = BIT_ULL(layer->level - 1);
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const unsigned long access_req = access_request;
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unsigned long access_bit;
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bool is_empty;
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/*
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* Records in @layer_masks which layer grants access to each
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* requested access.
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*/
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is_empty = true;
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for_each_set_bit(access_bit, &access_req,
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ARRAY_SIZE(*layer_masks)) {
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if (layer->access & BIT_ULL(access_bit))
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(*layer_masks)[access_bit] &= ~layer_bit;
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is_empty = is_empty && !(*layer_masks)[access_bit];
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}
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if (is_empty)
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return true;
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}
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return false;
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}
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/**
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* landlock_init_layer_masks - Initialize layer masks from an access request
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*
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* Populates @layer_masks such that for each access right in @access_request,
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* the bits for all the layers are set where this access right is handled.
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*
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* @domain: The domain that defines the current restrictions.
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* @access_request: The requested access rights to check.
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* @layer_masks: The layer masks to populate.
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*
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* Returns: An access mask where each access right bit is set which is handled
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* in any of the active layers in @domain.
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*/
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access_mask_t landlock_init_layer_masks(
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const struct landlock_ruleset *const domain,
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const access_mask_t access_request,
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layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
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{
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access_mask_t handled_accesses = 0;
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size_t layer_level;
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memset(layer_masks, 0, sizeof(*layer_masks));
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/* An empty access request can happen because of O_WRONLY | O_RDWR. */
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if (!access_request)
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return 0;
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/* Saves all handled accesses per layer. */
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for (layer_level = 0; layer_level < domain->num_layers; layer_level++) {
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const unsigned long access_req = access_request;
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unsigned long access_bit;
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for_each_set_bit(access_bit, &access_req,
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ARRAY_SIZE(*layer_masks)) {
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if (BIT_ULL(access_bit) &
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landlock_get_fs_access_mask(domain, layer_level)) {
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(*layer_masks)[access_bit] |=
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BIT_ULL(layer_level);
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handled_accesses |= BIT_ULL(access_bit);
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}
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}
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}
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return handled_accesses;
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}
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@ -267,4 +267,14 @@ landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
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LANDLOCK_ACCESS_FS_INITIALLY_DENIED;
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}
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bool landlock_unmask_layers(
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const struct landlock_rule *const rule,
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const access_mask_t access_request,
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layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS]);
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access_mask_t landlock_init_layer_masks(
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const struct landlock_ruleset *const domain,
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const access_mask_t access_request,
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layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS]);
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#endif /* _SECURITY_LANDLOCK_RULESET_H */
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