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fix: data races and check-then-act races in the CoinJoin server #7537

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fix: data races and check-then-act races in the CoinJoin server #7537

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5d22ec3
fix: make CoinJoin nSessionDenom atomic
PastaPastaPasta Aug 3, 2026
96cf376
fix: decide CoinJoin server state transitions under cs_coinjoin
PastaPastaPasta Aug 3, 2026
7443d02
fix: guard the CoinJoin session collaterals with cs_coinjoin
PastaPastaPasta Aug 3, 2026
cc27039
fix: revalidate the CoinJoin session before committing an entry
PastaPastaPasta Aug 3, 2026
aaa6d04
fix: mark multi-line CoinJoin LogPrint calls as continued for lint-logs
PastaPastaPasta Aug 3, 2026
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15 changes: 9 additions & 6 deletions src/coinjoin/client.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1229,8 +1229,9 @@ bool CCoinJoinClientSession::JoinExistingQueue(CAmount nBalanceNeedsAnonymized,
SetState(POOL_STATE_QUEUE);
nTimeLastSuccessfulStep = GetTime();
WalletCJLogPrint(m_wallet, /* Continued */
"CCoinJoinClientSession::JoinExistingQueue -- pending connection, masternode=%s, nSessionDenom=%d (%s)\n",
dmn->proTxHash.ToString(), nSessionDenom, CoinJoin::DenominationToString(nSessionDenom));
"CCoinJoinClientSession::JoinExistingQueue -- pending connection, masternode=%s, "
"nSessionDenom=%d (%s)\n",
dmn->proTxHash.ToString(), nSessionDenom.load(), CoinJoin::DenominationToString(nSessionDenom));
strAutoDenomResult = _("Trying to connect…");
return true;
}
Expand Down Expand Up @@ -1310,9 +1311,11 @@ bool CCoinJoinClientSession::StartNewQueue(CAmount nBalanceNeedsAnonymized, CCon
pendingDsaRequest = CPendingDsaRequest(dmn->proTxHash, CCoinJoinAccept(nSessionDenom, txMyCollateral));
SetState(POOL_STATE_QUEUE);
nTimeLastSuccessfulStep = GetTime();
WalletCJLogPrint( /* Continued */
m_wallet, "CCoinJoinClientSession::StartNewQueue -- pending connection, masternode=%s, nSessionDenom=%d (%s)\n",
dmn->proTxHash.ToString(), nSessionDenom, CoinJoin::DenominationToString(nSessionDenom));
WalletCJLogPrint(/* Continued */
m_wallet,
"CCoinJoinClientSession::StartNewQueue -- pending connection, masternode=%s, nSessionDenom=%d "
"(%s)\n",
dmn->proTxHash.ToString(), nSessionDenom.load(), CoinJoin::DenominationToString(nSessionDenom));
strAutoDenomResult = _("Trying to connect…");
return true;
}
Expand Down Expand Up @@ -1424,7 +1427,7 @@ bool CCoinJoinClientSession::SubmitDenominate(CConnman& connman)
return a.second > b.second || (a.second == b.second && a.first < b.first);
});

WalletCJLogPrint(m_wallet, "vecInputsByRounds for denom %d\n", nSessionDenom);
WalletCJLogPrint(m_wallet, "vecInputsByRounds for denom %d\n", nSessionDenom.load());
for (const auto& pair : vecInputsByRounds) {
WalletCJLogPrint(m_wallet, "vecInputsByRounds: rounds: %d, inputs: %d\n", pair.first, pair.second);
}
Expand Down
7 changes: 6 additions & 1 deletion src/coinjoin/coinjoin.h
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Original file line number Diff line number Diff line change
Expand Up @@ -342,7 +342,12 @@ class CCoinJoinBaseSession
PoolMessage& nMessageIDRet, bool* fConsumeCollateralRet) const;

public:
int nSessionDenom{0}; // Users must submit a denom matching this
// Users must submit a denom matching this. Atomic like its sibling session fields: it is
// written by the message-handling thread when a session opens and by either thread in
// SetNull(), and read unlocked by both plus RPC threads via GetJsonInfo().
// Note when logging: LogPrint() takes its arguments by const reference so a bare read works,
// but WalletCJLogPrint() takes them by value and needs an explicit .load().
std::atomic<int> nSessionDenom{0};

CCoinJoinBaseSession() = default;
virtual ~CCoinJoinBaseSession() = default;
Expand Down
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