2 files changed, 42 insertions, 10 deletions
diff --git a/fpdfsdk/fpdfformfill_embeddertest.cpp b/fpdfsdk/fpdfformfill_embeddertest.cpp
index 27b889085c..a1425153a1 100644
--- a/fpdfsdk/fpdfformfill_embeddertest.cpp
+++ b/fpdfsdk/fpdfformfill_embeddertest.cpp
@@ -134,4 +134,27 @@ TEST_F(FPDFFormFillEmbeddertest, BUG_620428) {
   EXPECT_STREQ(L"done", alerts[0].message.c_str());
 }
 
+TEST_F(FPDFFormFillEmbeddertest, BUG_634394) {
+  // Cancel timer inside timer callback.
+  EmbedderTestTimerHandlingDelegate delegate;
+  SetDelegate(&delegate);
+
+  EXPECT_TRUE(OpenDocument("bug_634394.pdf"));
+  FPDF_PAGE page = LoadPage(0);
+  EXPECT_TRUE(page);
+  DoOpenActions();
+
+  // Timers fire at most once per AdvanceTime(), allow intervals
+  // to fire several times if possible.
+  delegate.AdvanceTime(1000);
+  delegate.AdvanceTime(1000);
+  delegate.AdvanceTime(1000);
+  delegate.AdvanceTime(1000);
+  delegate.AdvanceTime(1000);
+  UnloadPage(page);
+
+  const auto& alerts = delegate.GetAlerts();
+  EXPECT_EQ(2U, alerts.size());
+}
+
 #endif  // PDF_ENABLE_V8
diff --git a/fpdfsdk/javascript/JS_Object.cpp b/fpdfsdk/javascript/JS_Object.cpp
index b0a307beb1..9ec316303d 100644
--- a/fpdfsdk/javascript/JS_Object.cpp
+++ b/fpdfsdk/javascript/JS_Object.cpp
@@ -115,16 +115,25 @@ void CJS_Timer::KillJSTimer() {
 
 // static
 void CJS_Timer::TimerProc(int idEvent) {
-  const auto it = GetGlobalTimerMap()->find(idEvent);
-  if (it != GetGlobalTimerMap()->end()) {
-    CJS_Timer* pTimer = it->second;
-    if (!pTimer->m_bProcessing) {
-      CFX_AutoRestorer<bool> scoped_processing(&pTimer->m_bProcessing);
-      pTimer->m_bProcessing = true;
-      if (pTimer->m_pEmbedObj)
-        pTimer->m_pEmbedObj->TimerProc(pTimer);
-    }
-  }
+  auto it = GetGlobalTimerMap()->find(idEvent);
+  if (it == GetGlobalTimerMap()->end())
+    return;
+
+  CJS_Timer* pTimer = it->second;
+  if (pTimer->m_bProcessing)
+    return;
+
+  pTimer->m_bProcessing = true;
+  if (pTimer->m_pEmbedObj)
+    pTimer->m_pEmbedObj->TimerProc(pTimer);
+
+  // Timer proc may have destroyed timer, find it again.
+  it = GetGlobalTimerMap()->find(idEvent);
+  if (it == GetGlobalTimerMap()->end())
+    return;
+
+  pTimer = it->second;
+  pTimer->m_bProcessing = false;
 }
 
 // static