diff --git a/fs/hfs/btree.c b/fs/hfs/btree.c
index 052f214..0609e71 100644
--- a/fs/hfs/btree.c
+++ b/fs/hfs/btree.c
@@ -45,11 +45,26 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id, btree_keycmp ke
 	case HFS_EXT_CNID:
 		hfs_inode_read_fork(tree->inode, mdb->drXTExtRec, mdb->drXTFlSize,
 				    mdb->drXTFlSize, be32_to_cpu(mdb->drXTClpSiz));
+		if (HFS_I(tree->inode)->alloc_blocks >
+					HFS_I(tree->inode)->first_blocks) {
+			printk(KERN_ERR "hfs: invalid btree extent records\n");
+			unlock_new_inode(tree->inode);
+			goto free_inode;
+		}
+
 		tree->inode->i_mapping->a_ops = &hfs_btree_aops;
 		break;
 	case HFS_CAT_CNID:
 		hfs_inode_read_fork(tree->inode, mdb->drCTExtRec, mdb->drCTFlSize,
 				    mdb->drCTFlSize, be32_to_cpu(mdb->drCTClpSiz));
+
+		if (!HFS_I(tree->inode)->first_blocks) {
+			printk(KERN_ERR "hfs: invalid btree extent records "
+								"(0 size).\n");
+			unlock_new_inode(tree->inode);
+			goto free_inode;
+		}
+
 		tree->inode->i_mapping->a_ops = &hfs_btree_aops;
 		break;
 	default:
@@ -58,11 +73,6 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id, btree_keycmp ke
 	}
 	unlock_new_inode(tree->inode);
 
-	if (!HFS_I(tree->inode)->first_blocks) {
-		printk(KERN_ERR "hfs: invalid btree extent records (0 size).\n");
-		goto free_inode;
-	}
-
 	mapping = tree->inode->i_mapping;
 	page = read_mapping_page(mapping, 0, NULL);
 	if (IS_ERR(page))