From 70c86561af6de764e117774fe207bb6aafd7728c Mon Sep 17 00:00:00 2001
From: moneromooo-monero <moneromooo-monero@users.noreply.github.com>
Date: Sun, 17 Apr 2016 14:43:16 +0100
Subject: [PATCH] blockchain: add missing overflow check for already generated
coins
When reaching the tail emission phase, the amount of coins will
eventually go over MONEY_SUPPLY, overflowing 64 bits. There was
a check added to blockchain_storage, but this was not ported to
the blockchain DB version.
Reported by smooth.
---
src/cryptonote_core/blockchain.cpp | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/src/cryptonote_core/blockchain.cpp b/src/cryptonote_core/blockchain.cpp
index 0569e748f..88ecb2dad 100644
--- a/src/cryptonote_core/blockchain.cpp
+++ b/src/cryptonote_core/blockchain.cpp
@@ -2713,7 +2713,11 @@ leave:
// populate various metadata about the block to be stored alongside it.
block_size = cumulative_block_size;
cumulative_difficulty = current_diffic;
- already_generated_coins = already_generated_coins + base_reward;
+ // In the "tail" state when the minimum subsidy (implemented in get_block_reward) is in effect, the number of
+ // coins will eventually exceed MONEY_SUPPLY and overflow a uint64. To prevent overflow, cap already_generated_coins
+ // at MONEY_SUPPLY. already_generated_coins is only used to compute the block subsidy and MONEY_SUPPLY yields a
+ // subsidy of 0 under the base formula and therefore the minimum subsidy >0 in the tail state.
+ already_generated_coins = base_reward < (MONEY_SUPPLY-already_generated_coins) ? already_generated_coins + base_reward : MONEY_SUPPLY;
if(m_db->height())
cumulative_difficulty += m_db->get_block_cumulative_difficulty(m_db->height() - 1);