From 5a7f33de565593aa9981d1c1f46ab72839209c92 Mon Sep 17 00:00:00 2001
From: "Christian Holler (:decoder)" <choller@mozilla.com>
Date: Fri, 19 Apr 2024 15:28:19 +0000
Subject: [PATCH] Bug 1883107 - Limit MessageTask blocking in fuzzing. r=nika

Differential Revision: https://phabricator.services.mozilla.com/D207715
---
 ipc/glue/MessageChannel.cpp | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/ipc/glue/MessageChannel.cpp b/ipc/glue/MessageChannel.cpp
index 16eb897175d1..544ce59b8ec2 100644
--- a/ipc/glue/MessageChannel.cpp
+++ b/ipc/glue/MessageChannel.cpp
@@ -1604,9 +1604,13 @@ nsresult MessageChannel::MessageTask::Run() {
     return NS_OK;
   }
 
+  Channel()->AssertWorkerThread();
+  mMonitor->AssertSameMonitor(*Channel()->mMonitor);
+
 #ifdef FUZZING_SNAPSHOT
   if (!mIsFuzzMsg) {
-    if (fuzzing::Nyx::instance().started()) {
+    if (fuzzing::Nyx::instance().started() && XRE_IsParentProcess() &&
+        Channel()->IsCrossProcess()) {
       // Once we started fuzzing, prevent non-fuzzing tasks from being
       // run and potentially blocking worker threads.
       //
@@ -1622,8 +1626,6 @@ nsresult MessageChannel::MessageTask::Run() {
   }
 #endif
 
-  Channel()->AssertWorkerThread();
-  mMonitor->AssertSameMonitor(*Channel()->mMonitor);
   proxy = Channel()->Listener()->GetLifecycleProxy();
   Channel()->RunMessage(proxy, *this);