Merge #11578: net: Add missing lock in ProcessHeadersMessage(...)

2530bf2 net: Add missing lock in ProcessHeadersMessage(...) (practicalswift)

Pull request description:

  Add missing lock in `ProcessHeadersMessage(...)`.

  Reading the variable `mapBlockIndex` requires holding the mutex `cs_main`.

  The new "Disconnect outbound peers relaying invalid headers" code added in commit 37886d5 and merged as part of #11568 two days ago did not lock `cs_main` prior to accessing `mapBlockIndex`.

Tree-SHA512: b799c234be8043d036183a00bc7867bbf3bd7ffe3baa94c88529da3b3cd0571c31ed11dadfaf29c5b8498341d6d0a3c928029a43b69f3267ef263682c91563a3

Author: laanwj

src/net_processing.cpp

@@ -1262,8 +1262,8 @@ bool static ProcessHeadersMessage(CNode *pfrom, CConnman *connman, const std::ve
     if (!ProcessNewBlockHeaders(headers, state, chainparams, &pindexLast, &first_invalid_header)) {
         int nDoS;
         if (state.IsInvalid(nDoS)) {
+            LOCK(cs_main);
             if (nDoS > 0) {
-                LOCK(cs_main);
                 Misbehaving(pfrom->GetId(), nDoS);
             }
             if (punish_duplicate_invalid && mapBlockIndex.find(first_invalid_header.GetHash()) != mapBlockIndex.end()) {