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LibWeb: Don't die when transferring the same MessagePort more than once

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One MessagePort can be entangled with another MessagePort, either in the
same agent, or in another agent.

In the same-agent case, the MessagePort objects point to each other via
the MessagePort::m_remote_port field.

In the separate-agent case, they live in separate processes entirely and
thus can't point at each other.

In both cases, the MessagePorts have an underlying transport channel,
which means they are "entangled". However, we can't assume that being
entangled means having a non-null m_remote_port.

This patch simply adds a missing null check for m_remote_port and thus
makes https://vscode.dev/ stop crashing with a null dereference.
This commit is contained in:
Andreas Kling
2025-08-28 12:57:55 +02:00
committed by Andreas Kling
parent e36cd6d82d
commit a26007f195
Notes: github-actions[bot] 2025-08-28 11:43:13 +00:00 
Author: https://github.com/awesomekling
Commit: https://github.com/LadybirdBrowser/ladybird/commit/a26007f1950
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/6010
3 changed files with 34 additions and 1 deletions
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27
Tests/LibWeb/Text/input/HTML/MessagePort-transfer-twice.html Normal file
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<!doctype html>
<script src="../include.js"></script>
<script>
asyncTest(done => {
function onFirst(e) {
const port = (e.data && e.data.port) || (e.ports && e.ports[0]);
if (!port) return;
println("first receipt: re-transferring same port");
window.removeEventListener("message", onFirst);
window.addEventListener("message", onSecond);
window.postMessage({ port }, "*", [port]);
}
function onSecond(e) {
println("we good");
done();
}
window.addEventListener("message", onFirst);
const { port1, port2 } = new MessageChannel();
port1.onmessage = e => println("main saw: " + e.data);
window.postMessage({ port: port2 }, "*", [port2]);
});
</script>