rpc: Fix wallet unload during walletpassphrase timeout

src/wallet/rpcwallet.cpp

@@ -1928,13 +1928,6 @@ static UniValue keypoolrefill(const JSONRPCRequest& request)
 }
 
 
-static void LockWallet(CWallet* pWallet)
-{
-    LOCK(pWallet->cs_wallet);
-    pWallet->nRelockTime = 0;
-    pWallet->Lock();
-}
-
 static UniValue walletpassphrase(const JSONRPCRequest& request)
 {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
@@ -2004,7 +1997,18 @@ static UniValue walletpassphrase(const JSONRPCRequest& request)
     pwallet->TopUpKeyPool();
 
     pwallet->nRelockTime = GetTime() + nSleepTime;
-    RPCRunLater(strprintf("lockwallet(%s)", pwallet->GetName()), std::bind(LockWallet, pwallet), nSleepTime);
+
+    // Keep a weak pointer to the wallet so that it is possible to unload the
+    // wallet before the following callback is called. If a valid shared pointer
+    // is acquired in the callback then the wallet is still loaded.
+    std::weak_ptr<CWallet> weak_wallet = wallet;
+    RPCRunLater(strprintf("lockwallet(%s)", pwallet->GetName()), [weak_wallet] {
+        if (auto shared_wallet = weak_wallet.lock()) {
+            LOCK(shared_wallet->cs_wallet);
+            shared_wallet->Lock();
+            shared_wallet->nRelockTime = 0;
+        }
+    }, nSleepTime);
 
     return NullUniValue;
 }