core: bugfix state change race condition in txpool (#3412)

The transaction pool keeps track of the current nonce in its local pendingState. When a
new block comes in the pendingState is reset. During the reset it fetches multiple times
the current state through the use of the currentState callback. When a second block comes
in during the reset its possible that the state changes during the reset. If that block
holds transactions that are currently in the pool the local pendingState that is used to
determine nonces can get out of sync.

2 files changed, 13 insertions, 5 deletions

diff --git a/internal/ethapi/api.go b/internal/ethapi/api.go
index a25eff5ed..fd86b6465 100644
--- a/internal/ethapi/api.go
+++ b/internal/ethapi/api.go
@@ -1273,8 +1273,12 @@ func (s *PublicTransactionPoolAPI) SignTransaction(ctx context.Context, args Sig
 
 // PendingTransactions returns the transactions that are in the transaction pool and have a from address that is one of
 // the accounts this node manages.
-func (s *PublicTransactionPoolAPI) PendingTransactions() []*RPCTransaction {
-	pending := s.b.GetPoolTransactions()
+func (s *PublicTransactionPoolAPI) PendingTransactions() ([]*RPCTransaction, error) {
+	pending, err := s.b.GetPoolTransactions()
+	if err != nil {
+		return nil, err
+	}
+
 	transactions := make([]*RPCTransaction, 0, len(pending))
 	for _, tx := range pending {
 		var signer types.Signer = types.HomesteadSigner{}
@@ -1286,13 +1290,17 @@ func (s *PublicTransactionPoolAPI) PendingTransactions() []*RPCTransaction {
 			transactions = append(transactions, newRPCPendingTransaction(tx))
 		}
 	}
-	return transactions
+	return transactions, nil
 }
 
 // Resend accepts an existing transaction and a new gas price and limit. It will remove the given transaction from the
 // pool and reinsert it with the new gas price and limit.
 func (s *PublicTransactionPoolAPI) Resend(ctx context.Context, tx Tx, gasPrice, gasLimit *rpc.HexNumber) (common.Hash, error) {
-	pending := s.b.GetPoolTransactions()
+	pending, err := s.b.GetPoolTransactions()
+	if err != nil {
+		return common.Hash{}, err
+	}
+
 	for _, p := range pending {
 		var signer types.Signer = types.HomesteadSigner{}
 		if p.Protected() {
diff --git a/internal/ethapi/backend.go b/internal/ethapi/backend.go
index 77df7eb8d..36d7e754b 100644
--- a/internal/ethapi/backend.go
+++ b/internal/ethapi/backend.go
@@ -55,7 +55,7 @@ type Backend interface {
 	// TxPool API
 	SendTx(ctx context.Context, signedTx *types.Transaction) error
 	RemoveTx(txHash common.Hash)
-	GetPoolTransactions() types.Transactions
+	GetPoolTransactions() (types.Transactions, error)
 	GetPoolTransaction(txHash common.Hash) *types.Transaction
 	GetPoolNonce(ctx context.Context, addr common.Address) (uint64, error)
 	Stats() (pending int, queued int)