contractcourt: fix race access to c.activeResolvers

contractcourt/channel_arbitrator.go

@@ -811,11 +811,8 @@ func (c *ChannelArbitrator) relaunchResolvers(commitSet *CommitSet,
 
 // Report returns htlc reports for the active resolvers.
 func (c *ChannelArbitrator) Report() []*ContractReport {
-	c.activeResolversLock.RLock()
-	defer c.activeResolversLock.RUnlock()
-
 	var reports []*ContractReport
-	for _, resolver := range c.activeResolvers {
+	for _, resolver := range c.resolvers() {
 		r, ok := resolver.(reportingContractResolver)
 		if !ok {
 			continue
@@ -1569,26 +1566,23 @@ func (c *ChannelArbitrator) findCommitmentDeadlineAndValue(heightHint uint32,
 // resolveContracts updates the activeResolvers list and starts to resolve each
 // contract concurrently, and launches them.
 func (c *ChannelArbitrator) resolveContracts(resolvers []ContractResolver) {
+	// Update the active contract resolvers.
 	c.activeResolversLock.Lock()
 	c.activeResolvers = resolvers
 	c.activeResolversLock.Unlock()
 
 	// Launch all resolvers.
 	c.launchResolvers()
 
-	for _, contract := range resolvers {
+	for _, contract := range c.resolvers() {
 		c.wg.Add(1)
 		go c.resolveContract(contract)
 	}
 }
 
 // launchResolvers launches all the active resolvers.
 func (c *ChannelArbitrator) launchResolvers() {
-	c.activeResolversLock.Lock()
-	resolvers := c.activeResolvers
-	c.activeResolversLock.Unlock()
-
-	for _, contract := range resolvers {
+	for _, contract := range c.resolvers() {
 		// If the contract is already resolved, there's no need to
 		// launch it again.
 		if contract.IsResolved() {
@@ -3426,3 +3420,14 @@ func (c *ChannelArbitrator) abandonForwards(htlcs fn.Set[uint64]) error {
 
 	return nil
 }
+
+// resolvers returns a copy of the active resolvers.
+func (c *ChannelArbitrator) resolvers() []ContractResolver {
+	c.activeResolversLock.Lock()
+	defer c.activeResolversLock.Unlock()
+
+	resolvers := make([]ContractResolver, 0, len(c.activeResolvers))
+	resolvers = append(resolvers, c.activeResolvers...)
+
+	return resolvers
+}