Re: [PATCH v8 03/12] landlock: Refactor merge/inherit_ruleset functions

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On 21/10/2022 17:26, Konstantin Meskhidze wrote:
Refactors merge_ruleset() and inherit_ruleset() functions to support

Refactor…

new rule types. This patch adds merge_tree() and inherit_tree()
helpers.

Each has key_type argument to choose a particular rb_tree

They use a specific ruleset's red-black tree according to a key type argument.

structure in a ruleset.

Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@xxxxxxxxxx>
---

Changes since v7:
* Adds missed lockdep_assert_held it inherit_tree() and merge_tree().
* Fixes comment.

Changes since v6:
* Refactors merge_ruleset() and inherit_ruleset() functions to support
   new rule types.
* Renames tree_merge() to merge_tree() (and reorder arguments), and
   tree_copy() to inherit_tree().

Changes since v5:
* Refactors some logic errors.
* Formats code with clang-format-14.

Changes since v4:
* None

---
  security/landlock/ruleset.c | 108 ++++++++++++++++++++++++------------
  1 file changed, 73 insertions(+), 35 deletions(-)

diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index 41de17d1869e..961ffe0c709e 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -302,36 +302,22 @@ static void put_hierarchy(struct landlock_hierarchy *hierarchy)
  	}
  }

-static int merge_ruleset(struct landlock_ruleset *const dst,
-			 struct landlock_ruleset *const src)
+static int merge_tree(struct landlock_ruleset *const dst,
+		      struct landlock_ruleset *const src,
+		      const enum landlock_key_type key_type)
  {
  	struct landlock_rule *walker_rule, *next_rule;
  	struct rb_root *src_root;
  	int err = 0;

  	might_sleep();
-	/* Should already be checked by landlock_merge_ruleset() */
-	if (WARN_ON_ONCE(!src))
-		return 0;
-	/* Only merge into a domain. */
-	if (WARN_ON_ONCE(!dst || !dst->hierarchy))
-		return -EINVAL;
+	lockdep_assert_held(&dst->lock);
+	lockdep_assert_held(&src->lock);

-	src_root = get_root(src, LANDLOCK_KEY_INODE);
+	src_root = get_root(src, key_type);
  	if (IS_ERR(src_root))
  		return PTR_ERR(src_root);

-	/* Locks @dst first because we are its only owner. */
-	mutex_lock(&dst->lock);
-	mutex_lock_nested(&src->lock, SINGLE_DEPTH_NESTING);
-
-	/* Stacks the new layer. */
-	if (WARN_ON_ONCE(src->num_layers != 1 || dst->num_layers < 1)) {
-		err = -EINVAL;
-		goto out_unlock;
-	}
-	dst->access_masks[dst->num_layers - 1] = src->access_masks[0];
-
  	/* Merges the @src tree. */
  	rbtree_postorder_for_each_entry_safe(walker_rule, next_rule, src_root,
  					     node) {
@@ -340,7 +326,7 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
  		} };
  		const struct landlock_id id = {
  			.key = walker_rule->key,
-			.type = LANDLOCK_KEY_INODE,
+			.type = key_type,
  		};

  		if (WARN_ON_ONCE(walker_rule->num_layers != 1))
@@ -351,8 +337,39 @@ static int merge_ruleset(struct landlock_ruleset *const dst,

  		err = insert_rule(dst, id, &layers, ARRAY_SIZE(layers));
  		if (err)
-			goto out_unlock;
+			return err;
+	}
+	return err;
+}
+
+static int merge_ruleset(struct landlock_ruleset *const dst,
+			 struct landlock_ruleset *const src)
+{
+	int err = 0;
+
+	might_sleep();
+	/* Should already be checked by landlock_merge_ruleset() */
+	if (WARN_ON_ONCE(!src))
+		return 0;
+	/* Only merge into a domain. */
+	if (WARN_ON_ONCE(!dst || !dst->hierarchy))
+		return -EINVAL;
+
+	/* Locks @dst first because we are its only owner. */
+	mutex_lock(&dst->lock);
+	mutex_lock_nested(&src->lock, SINGLE_DEPTH_NESTING);
+
+	/* Stacks the new layer. */
+	if (WARN_ON_ONCE(src->num_layers != 1 || dst->num_layers < 1)) {
+		err = -EINVAL;
+		goto out_unlock;
  	}
+	dst->access_masks[dst->num_layers - 1] = src->access_masks[0];
+
+	/* Merges the @src inode tree. */
+	err = merge_tree(dst, src, LANDLOCK_KEY_INODE);
+	if (err)
+		goto out_unlock;

  out_unlock:
  	mutex_unlock(&src->lock);
@@ -360,43 +377,64 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
  	return err;
  }

-static int inherit_ruleset(struct landlock_ruleset *const parent,
-			   struct landlock_ruleset *const child)
+static int inherit_tree(struct landlock_ruleset *const parent,
+			struct landlock_ruleset *const child,
+			const enum landlock_key_type key_type)
  {
  	struct landlock_rule *walker_rule, *next_rule;
  	struct rb_root *parent_root;
  	int err = 0;

  	might_sleep();
-	if (!parent)
-		return 0;
+	lockdep_assert_held(&parent->lock);
+	lockdep_assert_held(&parent->lock);

lockdep_assert_held(&child->lock);



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