Merge bitcoin#25983: Prevent data race for pathHandlers

4296dde Prevent data race for `pathHandlers` (Hennadii Stepanov)

Pull request description:

  Fixes bitcoin#19341.

ACKs for top commit:
  ryanofsky:
    Code review ACK 4296dde. This should protect the vector. It also seems to make the http_request_cb callback single threaded, but that seems ok, since it is just adding work queue items not actually processing requests.

Tree-SHA512: 1c3183100bbc80d8e83543da090b8f4521921cf30d444e3e4c87102bf7a1e67ccc4dfea7e9990ac49741b2a5708f259f4eced9d4049c20ae4e531461532a6aef

Author: MacroFake

src/httpserver.cpp

@@ -142,7 +142,8 @@ static std::vector<CSubNet> rpc_allow_subnets;
 //! Work queue for handling longer requests off the event loop thread
 static std::unique_ptr<WorkQueue<HTTPClosure>> g_work_queue{nullptr};
 //! Handlers for (sub)paths
-static std::vector<HTTPPathHandler> pathHandlers;
+static GlobalMutex g_httppathhandlers_mutex;
+static std::vector<HTTPPathHandler> pathHandlers GUARDED_BY(g_httppathhandlers_mutex);
 //! Bound listening sockets
 static std::vector<evhttp_bound_socket *> boundSockets;
 
@@ -243,6 +244,7 @@ static void http_request_cb(struct evhttp_request* req, void* arg)
     // Find registered handler for prefix
     std::string strURI = hreq->GetURI();
     std::string path;
+    LOCK(g_httppathhandlers_mutex);
     std::vector<HTTPPathHandler>::const_iterator i = pathHandlers.begin();
     std::vector<HTTPPathHandler>::const_iterator iend = pathHandlers.end();
     for (; i != iend; ++i) {
@@ -674,11 +676,13 @@ std::optional<std::string> GetQueryParameterFromUri(const char* uri, const std::
 void RegisterHTTPHandler(const std::string &prefix, bool exactMatch, const HTTPRequestHandler &handler)
 {
     LogPrint(BCLog::HTTP, "Registering HTTP handler for %s (exactmatch %d)\n", prefix, exactMatch);
+    LOCK(g_httppathhandlers_mutex);
     pathHandlers.push_back(HTTPPathHandler(prefix, exactMatch, handler));
 }
 
 void UnregisterHTTPHandler(const std::string &prefix, bool exactMatch)
 {
+    LOCK(g_httppathhandlers_mutex);
     std::vector<HTTPPathHandler>::iterator i = pathHandlers.begin();
     std::vector<HTTPPathHandler>::iterator iend = pathHandlers.end();
     for (; i != iend; ++i)