NetPlay: reject oversized input buffer messages

A NetPlay host could send an arbitrary buffer size to a client. The
client then tried to allocate input states until it reached that value.

Limit buffer sizes to the existing user-interface maximum. Invalid peer
values are ignored.

Source/Core/Core/NetPlayClient.cpp

@@ -754,8 +754,13 @@ void NetPlayClient::OnPadBuffer(sf::Packet& packet)
   u32 size = 0;
   packet >> size;
 
-  m_target_buffer_size = size;
-  m_dialog->OnPadBufferChanged(size);
+  if (size > MAX_TARGET_PAD_BUFFER_SIZE)
+  {
+    WARN_LOG_FMT(NETPLAY, "Ignoring invalid pad buffer size {}.", size);
+    return;
+  }
+
+  AdjustPadBufferSize(size);
 }
 
 void NetPlayClient::OnHostInputAuthority(sf::Packet& packet)

Source/Core/Core/NetPlayProto.h

@@ -244,6 +244,7 @@ enum class SyncCodeID : u8
 };
 
 constexpr u32 MAX_NAME_LENGTH = 30;
+constexpr u32 MAX_TARGET_PAD_BUFFER_SIZE = 99;
 constexpr size_t CHUNKED_DATA_UNIT_SIZE = 16384;
 constexpr u32 MAX_ENET_MTU = 1392;  // see https://github.com/lsalzman/enet/issues/132
 

Source/Core/DolphinQt/NetPlay/NetPlayDialog.cpp

@@ -33,6 +33,7 @@
 #include "Common/Logging/Log.h"
 #include "Common/TraversalClient.h"
 #include "Core/NetPlayCommon.h"
+#include "Core/NetPlayProto.h"
 
 #include "Core/Boot/Boot.h"
 #include "Core/Config/GraphicsSettings.h"
@@ -130,6 +131,7 @@ void NetPlayDialog::CreateMainLayout()
   m_game_button = new QPushButton;
   m_start_button = new QPushButton(tr("Start"));
   m_buffer_size_box = new QSpinBox;
+  m_buffer_size_box->setMaximum(NetPlay::MAX_TARGET_PAD_BUFFER_SIZE);
   m_buffer_label = new QLabel(tr("Buffer:"));
   m_quit_button = new QPushButton(tr("Quit"));
   m_splitter = new QSplitter(Qt::Horizontal);