From cb3bc3c493daacb0c90637c31c367597a84bcf69 Mon Sep 17 00:00:00 2001
From: Andreas Kling <andreas@ladybird.org>
Date: Wed, 21 Jan 2026 22:07:14 +0100
Subject: [PATCH] LibIPC: Move IPC message limits to a shared Limits.h header

This consolidates the message size and FD count limits into a single
header file that can be used by both the encoding and decoding sides
of the IPC layer.
---
 Libraries/LibIPC/Limits.h                   | 19 +++++++++++++++++++
 Libraries/LibIPC/TransportSocket.cpp        |  7 +------
 Libraries/LibIPC/TransportSocketWindows.cpp |  8 +++-----
 3 files changed, 23 insertions(+), 11 deletions(-)
 create mode 100644 Libraries/LibIPC/Limits.h

diff --git a/Libraries/LibIPC/Limits.h b/Libraries/LibIPC/Limits.h
new file mode 100644
index 0000000000..a49e2121e7
--- /dev/null
+++ b/Libraries/LibIPC/Limits.h
@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2026, Andreas Kling <andreas@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Types.h>
+
+namespace IPC {
+
+// Maximum size of an IPC message payload (64 MiB should be more than enough)
+static constexpr size_t MAX_MESSAGE_PAYLOAD_SIZE = 64 * MiB;
+
+// Maximum number of file descriptors per message
+static constexpr size_t MAX_MESSAGE_FD_COUNT = 128;
+
+}
diff --git a/Libraries/LibIPC/TransportSocket.cpp b/Libraries/LibIPC/TransportSocket.cpp
index a11491b2d8..e65cef01e2 100644
--- a/Libraries/LibIPC/TransportSocket.cpp
+++ b/Libraries/LibIPC/TransportSocket.cpp
@@ -10,6 +10,7 @@
 #include <AK/Types.h>
 #include <LibCore/Socket.h>
 #include <LibCore/System.h>
+#include <LibIPC/Limits.h>
 #include <LibIPC/TransportSocket.h>
 #include <LibThreading/Thread.h>
 
@@ -206,12 +207,6 @@ void TransportSocket::wait_until_readable()
     }
 }
 
-// Maximum size of an IPC message payload (64 MiB should be more than enough)
-static constexpr size_t MAX_MESSAGE_PAYLOAD_SIZE = 64 * MiB;
-
-// Maximum number of file descriptors per message
-static constexpr size_t MAX_MESSAGE_FD_COUNT = 128;
-
 // Maximum size of accumulated unprocessed bytes before we disconnect the peer
 static constexpr size_t MAX_UNPROCESSED_BUFFER_SIZE = 128 * MiB;
 
diff --git a/Libraries/LibIPC/TransportSocketWindows.cpp b/Libraries/LibIPC/TransportSocketWindows.cpp
index e9b08e1141..73387d6f4a 100644
--- a/Libraries/LibIPC/TransportSocketWindows.cpp
+++ b/Libraries/LibIPC/TransportSocketWindows.cpp
@@ -9,6 +9,7 @@
 #include <AK/Checked.h>
 #include <AK/Types.h>
 #include <LibIPC/HandleType.h>
+#include <LibIPC/Limits.h>
 #include <LibIPC/TransportSocketWindows.h>
 
 #include <AK/Windows.h>
@@ -107,9 +108,6 @@ ErrorOr<void> TransportSocketWindows::duplicate_handles(Bytes bytes, Vector<size
     return {};
 }
 
-// Maximum size of an IPC message payload (64 MiB should be more than enough)
-static constexpr size_t MAX_MESSAGE_SIZE = 64 * MiB;
-
 // Maximum size of accumulated unprocessed bytes before we disconnect the peer
 static constexpr size_t MAX_UNPROCESSED_BUFFER_SIZE = 128 * MiB;
 
@@ -206,8 +204,8 @@ TransportSocketWindows::ShouldShutdown TransportSocketWindows::read_as_many_mess
     while (index + sizeof(MessageHeader) <= m_unprocessed_bytes.size()) {
         MessageHeader header;
         memcpy(&header, m_unprocessed_bytes.data() + index, sizeof(MessageHeader));
-        if (header.size > MAX_MESSAGE_SIZE) {
-            dbgln("TransportSocketWindows: Rejecting message with size {} exceeding limit {}", header.size, MAX_MESSAGE_SIZE);
+        if (header.size > MAX_MESSAGE_PAYLOAD_SIZE) {
+            dbgln("TransportSocketWindows: Rejecting message with size {} exceeding limit {}", header.size, MAX_MESSAGE_PAYLOAD_SIZE);
             should_shutdown = ShouldShutdown::Yes;
             break;
         }