rpc: Serialize in getblock without cs_main

Author: MarcoFalke

src/rpc/blockchain.cpp

@@ -93,6 +93,7 @@ static int ComputeNextBlockAndDepth(const CBlockIndex* tip, const CBlockIndex* b
 
 UniValue blockheaderToJSON(const CBlockIndex* tip, const CBlockIndex* blockindex)
 {
+    // Serialize passed information without accessing chain state of the active chain!
     UniValue result(UniValue::VOBJ);
     result.pushKV("hash", blockindex->GetBlockHash().GetHex());
     const CBlockIndex* pnext;
@@ -119,6 +120,7 @@ UniValue blockheaderToJSON(const CBlockIndex* tip, const CBlockIndex* blockindex
 
 UniValue blockToJSON(const CBlock& block, const CBlockIndex* tip, const CBlockIndex* blockindex, bool txDetails)
 {
+    // Serialize passed information without accessing chain state of the active chain!
     UniValue result(UniValue::VOBJ);
     result.pushKV("hash", blockindex->GetBlockHash().GetHex());
     const CBlockIndex* pnext;
@@ -882,8 +884,6 @@ static UniValue getblock(const JSONRPCRequest& request)
         throw std::runtime_error(help.ToString());
     }
 
-    LOCK(cs_main);
-
     uint256 hash(ParseHashV(request.params[0], "blockhash"));
 
     int verbosity = 1;
@@ -894,12 +894,20 @@ static UniValue getblock(const JSONRPCRequest& request)
             verbosity = request.params[1].get_bool() ? 1 : 0;
     }
 
-    const CBlockIndex* pblockindex = LookupBlockIndex(hash);
-    if (!pblockindex) {
-        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
-    }
+    CBlock block;
+    const CBlockIndex* pblockindex;
+    const CBlockIndex* tip;
+    {
+        LOCK(cs_main);
+        pblockindex = LookupBlockIndex(hash);
+        tip = chainActive.Tip();
+
+        if (!pblockindex) {
+            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
+        }
 
-    const CBlock block = GetBlockChecked(pblockindex);
+        block = GetBlockChecked(pblockindex);
+    }
 
     if (verbosity <= 0)
     {
@@ -909,7 +917,7 @@ static UniValue getblock(const JSONRPCRequest& request)
         return strHex;
     }
 
-    return blockToJSON(block, chainActive.Tip(), pblockindex, verbosity >= 2);
+    return blockToJSON(block, tip, pblockindex, verbosity >= 2);
 }
 
 struct CCoinsStats