[PATCH v3 2/2] hfs: free cached B-tree nodes on hfs_btree_open() error path

[Mahmut Emin Kurhan]

The classic HFS driver has the same B-tree node leak as hfsplus: on the
hfs_btree_open() error path after hfs_bnode_find(tree, HFS_TREE_HEAD), an
errored head node left in tree->node_hash is not freed because free_tree:
does a bare kfree(tree) instead of walking the hash.

Apply the same fix: factor the node-hash freeing into hfs_bnode_hash_free()
and call it from hfs_btree_close() and the hfs_btree_open() error path. The
helper keeps the hash_lock serialization from commit dce0e0248205 ("hfs/hfsplus:
serialize B-tree close against folio release").

Found via coverage-guided fuzzing (syzkaller + kmemleak) by Noroxi.

Signed-off-by: Mahmut Emin Kurhan <guvenlik@xxxxxxxxxx>
---
 fs/hfs/btree.c | 40 +++++++++++++++++++++++-----------------
 1 file changed, 23 insertions(+), 17 deletions(-)

diff --git a/fs/hfs/btree.c b/fs/hfs/btree.c
index 4f0ddc76e8..140cdb5ec6 100644
--- a/fs/hfs/btree.c
+++ b/fs/hfs/btree.c
@@ -131,6 +131,27 @@ static int hfs_bmap_clear_bit(struct hfs_bnode *node, u32 node_bit_idx)
 }
 
 /* Get a reference to a B*Tree and do some initial checks */
+static void hfs_bnode_hash_free(struct hfs_btree *tree)
+{
+	struct hfs_bnode *node;
+	int i;
+
+	for (i = 0; i < NODE_HASH_SIZE; i++) {
+		spin_lock(&tree->hash_lock);
+		while ((node = tree->node_hash[i])) {
+			hfs_bnode_unhash(node);
+			spin_unlock(&tree->hash_lock);
+			if (atomic_read(&node->refcnt))
+				pr_err("node %d:%d still has %d user(s)!\n",
+				       node->tree->cnid, node->this,
+				       atomic_read(&node->refcnt));
+			hfs_bnode_free(node);
+			spin_lock(&tree->hash_lock);
+		}
+		spin_unlock(&tree->hash_lock);
+	}
+}
+
 struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id, btree_keycmp keycmp)
 {
 	struct hfs_btree *tree;
@@ -296,6 +317,7 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id, btree_keycmp ke
 	tree->inode->i_mapping->a_ops = &hfs_aops;
 	iput(tree->inode);
 free_tree:
+	hfs_bnode_hash_free(tree);
 	kfree(tree);
 	return NULL;
 }
@@ -303,26 +325,10 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id, btree_keycmp ke
 /* Release resources used by a btree */
 void hfs_btree_close(struct hfs_btree *tree)
 {
-	struct hfs_bnode *node;
-	int i;
-
 	if (!tree)
 		return;
 
-	for (i = 0; i < NODE_HASH_SIZE; i++) {
-		spin_lock(&tree->hash_lock);
-		while ((node = tree->node_hash[i])) {
-			hfs_bnode_unhash(node);
-			spin_unlock(&tree->hash_lock);
-			if (atomic_read(&node->refcnt))
-				pr_err("node %d:%d still has %d user(s)!\n",
-				       node->tree->cnid, node->this,
-				       atomic_read(&node->refcnt));
-			hfs_bnode_free(node);
-			spin_lock(&tree->hash_lock);
-		}
-		spin_unlock(&tree->hash_lock);
-	}
+	hfs_bnode_hash_free(tree);
 	iput(tree->inode);
 	kfree(tree);
 }
-- 
2.43.0