[PATCH 3/8] maple_tree: fix freeing of nodes in rcu mode

["Liam R. Howlett" <Liam.Howlett@oracle.com>]

From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>

The walk to destroy the nodes was not always setting the node type and
would result in a destroy method potentially using the values as nodes.
Avoid this by setting the correct node types.  This is necessary for the
RCU mode of the maple tree.

Link: https://lkml.kernel.org/r/20230227173632.3292573-4-surenb@google.com
Cc: <Stable@vger.kernel.org>
Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
---
 lib/maple_tree.c | 73 ++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 62 insertions(+), 11 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 089cd76ec379..44d6ce30b28e 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -902,6 +902,44 @@ static inline void ma_set_meta(struct maple_node *mn, enum maple_type mt,
 	meta->end = end;
 }
 
+/*
+ * mas_clear_meta() - clear the metadata information of a node, if it exists
+ * @mas: The maple state
+ * @mn: The maple node
+ * @mt: The maple node type
+ * @offset: The offset of the highest sub-gap in this node.
+ * @end: The end of the data in this node.
+ */
+static inline void mas_clear_meta(struct ma_state *mas, struct maple_node *mn,
+				  enum maple_type mt)
+{
+	struct maple_metadata *meta;
+	unsigned long *pivots;
+	void __rcu **slots;
+	void *next;
+
+	switch (mt) {
+	case maple_range_64:
+		pivots = mn->mr64.pivot;
+		if (unlikely(pivots[MAPLE_RANGE64_SLOTS - 2])) {
+			slots = mn->mr64.slot;
+			next = mas_slot_locked(mas, slots,
+					       MAPLE_RANGE64_SLOTS - 1);
+			if (unlikely((mte_to_node(next) && mte_node_type(next))))
+				return; /* The last slot is a node, no metadata */
+		}
+		fallthrough;
+	case maple_arange_64:
+		meta = ma_meta(mn, mt);
+		break;
+	default:
+		return;
+	}
+
+	meta->gap = 0;
+	meta->end = 0;
+}
+
 /*
  * ma_meta_end() - Get the data end of a node from the metadata
  * @mn: The maple node
@@ -5455,20 +5493,22 @@ static inline int mas_rev_alloc(struct ma_state *mas, unsigned long min,
  * mas_dead_leaves() - Mark all leaves of a node as dead.
  * @mas: The maple state
  * @slots: Pointer to the slot array
+ * @type: The maple node type
  *
  * Must hold the write lock.
  *
  * Return: The number of leaves marked as dead.
  */
 static inline
-unsigned char mas_dead_leaves(struct ma_state *mas, void __rcu **slots)
+unsigned char mas_dead_leaves(struct ma_state *mas, void __rcu **slots,
+			      enum maple_type mt)
 {
 	struct maple_node *node;
 	enum maple_type type;
 	void *entry;
 	int offset;
 
-	for (offset = 0; offset < mt_slot_count(mas->node); offset++) {
+	for (offset = 0; offset < mt_slots[mt]; offset++) {
 		entry = mas_slot_locked(mas, slots, offset);
 		type = mte_node_type(entry);
 		node = mte_to_node(entry);
@@ -5487,14 +5527,13 @@ unsigned char mas_dead_leaves(struct ma_state *mas, void __rcu **slots)
 
 static void __rcu **mas_dead_walk(struct ma_state *mas, unsigned char offset)
 {
-	struct maple_node *node, *next;
+	struct maple_node *next;
 	void __rcu **slots = NULL;
 
 	next = mas_mn(mas);
 	do {
-		mas->node = ma_enode_ptr(next);
-		node = mas_mn(mas);
-		slots = ma_slots(node, node->type);
+		mas->node = mt_mk_node(next, next->type);
+		slots = ma_slots(next, next->type);
 		next = mas_slot_locked(mas, slots, offset);
 		offset = 0;
 	} while (!ma_is_leaf(next->type));
@@ -5558,11 +5597,14 @@ static inline void __rcu **mas_destroy_descend(struct ma_state *mas,
 		node = mas_mn(mas);
 		slots = ma_slots(node, mte_node_type(mas->node));
 		next = mas_slot_locked(mas, slots, 0);
-		if ((mte_dead_node(next)))
+		if ((mte_dead_node(next))) {
+			mte_to_node(next)->type = mte_node_type(next);
 			next = mas_slot_locked(mas, slots, 1);
+		}
 
 		mte_set_node_dead(mas->node);
 		node->type = mte_node_type(mas->node);
+		mas_clear_meta(mas, node, node->type);
 		node->piv_parent = prev;
 		node->parent_slot = offset;
 		offset = 0;
@@ -5582,13 +5624,18 @@ static void mt_destroy_walk(struct maple_enode *enode, unsigned char ma_flags,
 
 	MA_STATE(mas, &mt, 0, 0);
 
-	if (mte_is_leaf(enode))
+	mas.node = enode;
+	if (mte_is_leaf(enode)) {
+		node->type = mte_node_type(enode);
 		goto free_leaf;
+	}
 
+	ma_flags &= ~MT_FLAGS_LOCK_MASK;
 	mt_init_flags(&mt, ma_flags);
 	mas_lock(&mas);
 
-	mas.node = start = enode;
+	mte_to_node(enode)->ma_flags = ma_flags;
+	start = enode;
 	slots = mas_destroy_descend(&mas, start, 0);
 	node = mas_mn(&mas);
 	do {
@@ -5596,7 +5643,8 @@ static void mt_destroy_walk(struct maple_enode *enode, unsigned char ma_flags,
 		unsigned char offset;
 		struct maple_enode *parent, *tmp;
 
-		node->slot_len = mas_dead_leaves(&mas, slots);
+		node->type = mte_node_type(mas.node);
+		node->slot_len = mas_dead_leaves(&mas, slots, node->type);
 		if (free)
 			mt_free_bulk(node->slot_len, slots);
 		offset = node->parent_slot + 1;
@@ -5620,7 +5668,8 @@ static void mt_destroy_walk(struct maple_enode *enode, unsigned char ma_flags,
 	} while (start != mas.node);
 
 	node = mas_mn(&mas);
-	node->slot_len = mas_dead_leaves(&mas, slots);
+	node->type = mte_node_type(mas.node);
+	node->slot_len = mas_dead_leaves(&mas, slots, node->type);
 	if (free)
 		mt_free_bulk(node->slot_len, slots);
 
@@ -5630,6 +5679,8 @@ static void mt_destroy_walk(struct maple_enode *enode, unsigned char ma_flags,
 free_leaf:
 	if (free)
 		mt_free_rcu(&node->rcu);
+	else
+		mas_clear_meta(&mas, node, node->type);
 }
 
 /*
-- 
2.39.2