On 16/01/2023 09:58, Konstantin Meskhidze wrote:
This patch renames and moves unmask_layers() and init_layer_masks()
helpers to ruleset.c to share them with Landlock network implementation
in following commits.
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@xxxxxxxxxx>
---
Changes since v8:
* Refactors commit message.
* Adds "landlock_" prefix for moved helpers.
Changes since v7:
* Refactors commit message.
Changes since v6:
* Moves get_handled_accesses() helper from ruleset.c back to fs.c,
cause it's not used in coming network commits.
Changes since v5:
* Splits commit.
* Moves init_layer_masks() and get_handled_accesses() helpers
to ruleset.c and makes then non-static.
* Formats code with clang-format-14.
---
[...]
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index 3e1cffda128e..22590cac3d56 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -572,3 +572,101 @@ landlock_find_rule(const struct landlock_ruleset *const ruleset,
}
return NULL;
}
+
+/*
+ * @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 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])
+{
+ 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 <execute> + /a <read> => /a/b <execute + read>
+ */
+ 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;
+}
+
+/*
Please keep the original "/**"
+ * init_layer_masks - Initialize layer masks from an access request
+ *
+ * Populates @layer_masks such that for each access right in @access_request,
+ * the bits for all the layers are set where this access right is handled.
+ *
+ * @domain: The domain that defines the current restrictions.
+ * @access_request: The requested access rights to check.
+ * @layer_masks: The layer masks to populate.
+ *
+ * Returns: An access mask where each access right bit is set which is handled
+ * in any of the active layers in @domain.
+ */
