Bugfix: only track UTXO modification after lookup

Otherwise, if CCoinsViewCache::ModifyCoins throws an exception in between setting hasModifier and constructing the CCoinsModifier, the cache ends up in an inconsistent state, resulting in an assert failure in the next modification. Bug discovered by Wladimir J. van der Laan.
TrezarCoin · Jan 4, 2015 · 02bced1 · 02bced1
1 parent a99ef7d
commit 02bced1
Showing 1 changed file with 4 additions and 2 deletions.
diff --git a/src/coins.cpp b/src/coins.cpp
@@ -106,7 +106,6 @@ bool CCoinsViewCache::GetCoins(const uint256 &txid, CCoins &coins) const {
 
 CCoinsModifier CCoinsViewCache::ModifyCoins(const uint256 &txid) {
     assert(!hasModifier);
-    hasModifier = true;
     std::pair<CCoinsMap::iterator, bool> ret = cacheCoins.insert(std::make_pair(txid, CCoinsCacheEntry()));
     if (ret.second) {
         if (!base->GetCoins(txid, ret.first->second.coins)) {
@@ -247,7 +246,10 @@ double CCoinsViewCache::GetPriority(const CTransaction &tx, int nHeight) const
     return tx.ComputePriority(dResult);
 }
 
-CCoinsModifier::CCoinsModifier(CCoinsViewCache& cache_, CCoinsMap::iterator it_) : cache(cache_), it(it_) {}
+CCoinsModifier::CCoinsModifier(CCoinsViewCache& cache_, CCoinsMap::iterator it_) : cache(cache_), it(it_) {
+    assert(!cache.hasModifier);
+    cache.hasModifier = true;
+}
 
 CCoinsModifier::~CCoinsModifier()
 {