From 11bbc660823246b9fc25e4b994121e30a9f17306 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A9ter=20Szil=C3=A1gyi?= <peterke@gmail.com>
Date: Wed, 8 Aug 2018 17:16:38 +0300
Subject: eth, trie: fix tracer GC which accidentally pruned the metaroot

---
 trie/database.go | 5 +++++
 1 file changed, 5 insertions(+)

(limited to 'trie')

diff --git a/trie/database.go b/trie/database.go
index 7df45fe2d..d0691b637 100644
--- a/trie/database.go
+++ b/trie/database.go
@@ -431,6 +431,11 @@ func (db *Database) reference(child common.Hash, parent common.Hash) {
 
 // Dereference removes an existing reference from a root node.
 func (db *Database) Dereference(root common.Hash) {
+	// Sanity check to ensure that the meta-root is not removed
+	if root == (common.Hash{}) {
+		log.Error("Attempted to dereference the trie cache meta root")
+		return
+	}
 	db.lock.Lock()
 	defer db.lock.Unlock()
 
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