From c3778db14df34e88bfd3663b2b3fb54ead633402 Mon Sep 17 00:00:00 2001
From: Moonchild <moonchild@palemoon.org>
Date: Wed, 21 Oct 2020 20:35:07 +0000
Subject: [DOM Fetch] Improve stability of Fetch API.

---
 dom/fetch/FetchDriver.cpp | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/dom/fetch/FetchDriver.cpp b/dom/fetch/FetchDriver.cpp
index fd1e99a2b..d028ffdba 100644
--- a/dom/fetch/FetchDriver.cpp
+++ b/dom/fetch/FetchDriver.cpp
@@ -709,10 +709,12 @@ FetchDriver::OnDataAvailable(nsIRequest* aRequest,
   // about races.
 
   if (mObserver) {
+    // Need to keep mObserver alive.
+    RefPtr<FetchDriverObserver> observer = mObserver;
     if (NS_IsMainThread()) {
-      mObserver->OnDataAvailable();
+      observer->OnDataAvailable();
     } else {
-      RefPtr<Runnable> runnable = new DataAvailableRunnable(mObserver);
+      RefPtr<Runnable> runnable = new DataAvailableRunnable(observer);
       nsresult rv = NS_DispatchToMainThread(runnable);
       if (NS_WARN_IF(NS_FAILED(rv))) {
         return rv;
@@ -720,12 +722,15 @@ FetchDriver::OnDataAvailable(nsIRequest* aRequest,
     }
   }
 
-  uint32_t aRead;
+  // Explicitly initialized to 0 because in some cases nsStringInputStream may
+  // not write to aRead.
+  uint32_t aRead = 0;
   MOZ_ASSERT(mResponse);
   MOZ_ASSERT(mPipeOutputStream);
 
   // From "Main Fetch" step 17: SRI-part2.
-  if (mResponse->Type() != ResponseType::Error &&
+  if (mResponse &&
+      mResponse->Type() != ResponseType::Error &&
       !mRequest->GetIntegrity().IsEmpty()) {
     MOZ_ASSERT(mSRIDataVerifier);
 
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