landlock: Refactor layer helpers

Add a new key_type argument to the landlock_init_layer_masks() helper.
Add a masks_array_size argument to the landlock_unmask_layers() helper.
These modifications support implementing new rule types in the next
Landlock versions.

Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Link: https://lore.kernel.org/r/20231026014751.414649-7-konstantin.meskhidze@huawei.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>

diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index e6a19ff1765af4bf1ab1fe35afae2bd130235e55..bc7c126deea2f77428e8df76ba2132259557964c 100644 (file)
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -442,20 +442,22 @@ static bool is_access_to_paths_allowed(
        }
 
        if (unlikely(dentry_child1)) {
-               landlock_unmask_layers(find_rule(domain, dentry_child1),
-                                      landlock_init_layer_masks(
-                                              domain, LANDLOCK_MASK_ACCESS_FS,
-                                              &_layer_masks_child1),
-                                      &_layer_masks_child1);
+               landlock_unmask_layers(
+                       find_rule(domain, dentry_child1),
+                       landlock_init_layer_masks(
+                               domain, LANDLOCK_MASK_ACCESS_FS,
+                               &_layer_masks_child1, LANDLOCK_KEY_INODE),
+                       &_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)) {
-               landlock_unmask_layers(find_rule(domain, dentry_child2),
-                                      landlock_init_layer_masks(
-                                              domain, LANDLOCK_MASK_ACCESS_FS,
-                                              &_layer_masks_child2),
-                                      &_layer_masks_child2);
+               landlock_unmask_layers(
+                       find_rule(domain, dentry_child2),
+                       landlock_init_layer_masks(
+                               domain, LANDLOCK_MASK_ACCESS_FS,
+                               &_layer_masks_child2, LANDLOCK_KEY_INODE),
+                       &_layer_masks_child2, ARRAY_SIZE(_layer_masks_child2));
                layer_masks_child2 = &_layer_masks_child2;
                child2_is_directory = d_is_dir(dentry_child2);
        }
@@ -508,14 +510,15 @@ static bool is_access_to_paths_allowed(
 
                rule = find_rule(domain, walker_path.dentry);
                allowed_parent1 = landlock_unmask_layers(
-                       rule, access_masked_parent1, layer_masks_parent1);
+                       rule, access_masked_parent1, layer_masks_parent1,
+                       ARRAY_SIZE(*layer_masks_parent1));
                allowed_parent2 = landlock_unmask_layers(
-                       rule, access_masked_parent2, layer_masks_parent2);
+                       rule, access_masked_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)) {
@@ -554,8 +557,8 @@ static inline int check_access_path(const struct landlock_ruleset *const domain,
 {
        layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {};
 
-       access_request =
-               landlock_init_layer_masks(domain, access_request, &layer_masks);
+       access_request = landlock_init_layer_masks(
+               domain, access_request, &layer_masks, LANDLOCK_KEY_INODE);
        if (is_access_to_paths_allowed(domain, path, access_request,
                                       &layer_masks, NULL, 0, NULL, NULL))
                return 0;
@@ -641,7 +644,8 @@ static bool collect_domain_accesses(
                return true;
 
        access_dom = landlock_init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
-                                              layer_masks_dom);
+                                              layer_masks_dom,
+                                              LANDLOCK_KEY_INODE);
 
        dget(dir);
        while (true) {
@@ -649,7 +653,8 @@ static bool collect_domain_accesses(
 
                /* Gets all layers allowing all domain accesses. */
                if (landlock_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.
@@ -764,7 +769,7 @@ static int current_check_refer_path(struct dentry *const old_dentry,
                 */
                access_request_parent1 = landlock_init_layer_masks(
                        dom, access_request_parent1 | access_request_parent2,
-                       &layer_masks_parent1);
+                       &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))
@@ -1140,7 +1145,7 @@ static int hook_file_open(struct file *const file)
        if (is_access_to_paths_allowed(
                    dom, &file->f_path,
                    landlock_init_layer_masks(dom, full_access_request,
-                                             &layer_masks),
+                                             &layer_masks, LANDLOCK_KEY_INODE),
                    &layer_masks, NULL, 0, NULL, NULL)) {
                allowed_access = full_access_request;
        } else {

diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index 28ffeedd21d6caf05ece508301488556a3af8bb8..e36c5c3322429b38c8920244fadc066be72dc35b 100644 (file)
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -573,14 +573,15 @@ landlock_find_rule(const struct landlock_ruleset *const ruleset,
 /*
  * @layer_masks is read and may be updated according to the access request and
  * the matching rule.
+ * @masks_array_size must be equal to ARRAY_SIZE(*layer_masks).
  *
  * Returns true if the request is allowed (i.e. relevant layer masks for the
  * request are empty).
  */
-bool landlock_unmask_layers(
-       const struct landlock_rule *const rule,
-       const access_mask_t access_request,
-       layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
+bool landlock_unmask_layers(const struct landlock_rule *const rule,
+                           const access_mask_t access_request,
+                           layer_mask_t (*const layer_masks)[],
+                           const size_t masks_array_size)
 {
        size_t layer_level;
 
@@ -612,8 +613,7 @@ bool landlock_unmask_layers(
                 * requested access.
                 */
                is_empty = true;
-               for_each_set_bit(access_bit, &access_req,
-                                ARRAY_SIZE(*layer_masks)) {
+               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];
@@ -624,6 +624,10 @@ bool landlock_unmask_layers(
        return false;
 }
 
+typedef access_mask_t
+get_access_mask_t(const struct landlock_ruleset *const ruleset,
+                 const u16 layer_level);
+
 /**
  * landlock_init_layer_masks - Initialize layer masks from an access request
  *
@@ -633,19 +637,34 @@ bool landlock_unmask_layers(
  * @domain: The domain that defines the current restrictions.
  * @access_request: The requested access rights to check.
  * @layer_masks: The layer masks to populate.
+ * @key_type: The key type to switch between access masks of different types.
  *
  * Returns: An access mask where each access right bit is set which is handled
  * in any of the active layers in @domain.
  */
-access_mask_t landlock_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
+landlock_init_layer_masks(const struct landlock_ruleset *const domain,
+                         const access_mask_t access_request,
+                         layer_mask_t (*const layer_masks)[],
+                         const enum landlock_key_type key_type)
 {
        access_mask_t handled_accesses = 0;
-       size_t layer_level;
+       size_t layer_level, num_access;
+       get_access_mask_t *get_access_mask;
+
+       switch (key_type) {
+       case LANDLOCK_KEY_INODE:
+               get_access_mask = landlock_get_fs_access_mask;
+               num_access = LANDLOCK_NUM_ACCESS_FS;
+               break;
+       default:
+               WARN_ON_ONCE(1);
+               return 0;
+       }
+
+       memset(layer_masks, 0,
+              array_size(sizeof((*layer_masks)[0]), num_access));
 
-       memset(layer_masks, 0, sizeof(*layer_masks));
        /* An empty access request can happen because of O_WRONLY | O_RDWR. */
        if (!access_request)
                return 0;
@@ -655,10 +674,9 @@ access_mask_t landlock_init_layer_masks(
                const unsigned long access_req = access_request;
                unsigned long access_bit;
 
-               for_each_set_bit(access_bit, &access_req,
-                                ARRAY_SIZE(*layer_masks)) {
+               for_each_set_bit(access_bit, &access_req, num_access) {
                        if (BIT_ULL(access_bit) &
-                           landlock_get_fs_access_mask(domain, layer_level)) {
+                           get_access_mask(domain, layer_level)) {
                                (*layer_masks)[access_bit] |=
                                        BIT_ULL(layer_level);
                                handled_accesses |= BIT_ULL(access_bit);

diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index 760e049f3e0a93a5e46832325b164fee33fb221f..7107ce7da39dd2f44ebd2cfc60bf5e90c703d0d1 100644 (file)
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -267,14 +267,15 @@ landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
               LANDLOCK_ACCESS_FS_INITIALLY_DENIED;
 }
 
-bool landlock_unmask_layers(
-       const struct landlock_rule *const rule,
-       const access_mask_t access_request,
-       layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS]);
+bool landlock_unmask_layers(const struct landlock_rule *const rule,
+                           const access_mask_t access_request,
+                           layer_mask_t (*const layer_masks)[],
+                           const size_t masks_array_size);
 
-access_mask_t landlock_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
+landlock_init_layer_masks(const struct landlock_ruleset *const domain,
+                         const access_mask_t access_request,
+                         layer_mask_t (*const layer_masks)[],
+                         const enum landlock_key_type key_type);
 
 #endif /* _SECURITY_LANDLOCK_RULESET_H */