core: fix setHead, panics

Author: MariusVanDerWijden

core/blockchain.go

@@ -467,7 +467,7 @@ func (bc *BlockChain) loadLastState() error {
 		}
 	}
 
-	// Restore the last known finalized block amd safe block
+	// Restore the last known finalized block and safe block
 	// Note: the safe block is not stored on disk and it is set to the last
 	// known finalized block on startup
 	if head := rawdb.ReadFinalizedBlockHash(bc.db); head != (common.Hash{}) {
@@ -511,14 +511,23 @@ func (bc *BlockChain) SetHead(head uint64) error {
 // SetFinalized sets the finalized block.
 func (bc *BlockChain) SetFinalized(block *types.Block) {
 	bc.currentFinalizedBlock.Store(block)
-	rawdb.WriteFinalizedBlockHash(bc.db, block.Hash())
-	headFinalizedBlockGauge.Update(int64(block.NumberU64()))
+	if block != nil {
+		rawdb.WriteFinalizedBlockHash(bc.db, block.Hash())
+		headFinalizedBlockGauge.Update(int64(block.NumberU64()))
+	} else {
+		rawdb.WriteFinalizedBlockHash(bc.db, common.Hash{})
+		headFinalizedBlockGauge.Update(0)
+	}
 }
 
 // SetSafe sets the safe block.
 func (bc *BlockChain) SetSafe(block *types.Block) {
 	bc.currentSafeBlock.Store(block)
-	headSafeBlockGauge.Update(int64(block.NumberU64()))
+	if block != nil {
+		headSafeBlockGauge.Update(int64(block.NumberU64()))
+	} else {
+		headSafeBlockGauge.Update(0)
+	}
 }
 
 // setHeadBeyondRoot rewinds the local chain to a new head with the extra condition
@@ -676,6 +685,16 @@ func (bc *BlockChain) setHeadBeyondRoot(head uint64, root common.Hash, repair bo
 	bc.txLookupCache.Purge()
 	bc.futureBlocks.Purge()
 
+	// Clear safe block, finalized block if needed
+	if safe := bc.CurrentSafeBlock(); safe != nil && head < safe.NumberU64() {
+		log.Warn("SetHead invalidated safe block")
+		bc.SetSafe(nil)
+	}
+	if finalized := bc.CurrentFinalizedBlock(); finalized != nil && head < finalized.NumberU64() {
+		log.Error("SetHead invalidated finalized block")
+		bc.SetFinalized(nil)
+	}
+
 	return rootNumber, bc.loadLastState()
 }
 

eth/api_backend.go

@@ -74,10 +74,18 @@ func (b *EthAPIBackend) HeaderByNumber(ctx context.Context, number rpc.BlockNumb
 		return b.eth.blockchain.CurrentBlock().Header(), nil
 	}
 	if number == rpc.FinalizedBlockNumber {
-		return b.eth.blockchain.CurrentFinalizedBlock().Header(), nil
+		block := b.eth.blockchain.CurrentFinalizedBlock()
+		if block != nil {
+			return block.Header(), nil
+		}
+		return nil, errors.New("finalized block not found")
 	}
 	if number == rpc.SafeBlockNumber {
-		return b.eth.blockchain.CurrentSafeBlock().Header(), nil
+		block := b.eth.blockchain.CurrentSafeBlock()
+		if block != nil {
+			return block.Header(), nil
+		}
+		return nil, errors.New("safe block not found")
 	}
 	return b.eth.blockchain.GetHeaderByNumber(uint64(number)), nil
 }