From cbf190562114641a9d82d1a11b7bba2bb9fcff1e Mon Sep 17 00:00:00 2001
From: Tim Ledbetter <tim.ledbetter@ladybird.org>
Date: Tue, 30 Jul 2024 15:04:32 +0100
Subject: [PATCH] LibWeb: Account for header size when reading MessagePort
 message payload

Previously, the fact that this wasn't accounted for could lead to a
crash when large messages were received.

(cherry picked from commit 34e465a67e41b82b276050dde0b4b321c2cf1b18)
---
 Userland/Libraries/LibWeb/HTML/MessagePort.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Userland/Libraries/LibWeb/HTML/MessagePort.cpp b/Userland/Libraries/LibWeb/HTML/MessagePort.cpp
index f3412cb9e0..e2ff9f0f99 100644
--- a/Userland/Libraries/LibWeb/HTML/MessagePort.cpp
+++ b/Userland/Libraries/LibWeb/HTML/MessagePort.cpp
@@ -279,7 +279,7 @@ ErrorOr<MessagePort::ParseDecision> MessagePort::parse_message()
         [[fallthrough]];
     }
     case SocketState::Data: {
-        if (num_bytes_ready < m_socket_incoming_message_size)
+        if (num_bytes_ready < HEADER_SIZE + m_socket_incoming_message_size)
             return ParseDecision::NotEnoughData;
 
         auto payload = m_buffered_data.span().slice(HEADER_SIZE, m_socket_incoming_message_size);