Fix heap use after free in CPDFSDK_Annot::GetPDFAnnot.

Use two seperate loops to kill current focus annot and to release annots
in current page. Loop to kill current focus annot is run first, so it
will not access deleted annots.

BUG=507316

R=tsepez@chromium.org

TEST=Reproduction steps mentioned in issue 507316 should not crash
     chrome.
     Unit test added to pdfium.
     Run pdfium_embeddertests.exe.

Review URL: https://codereview.chromium.org/1312313006 .

1 files changed, 12 insertions, 0 deletions

diff --git a/fpdfsdk/src/fpdfformfill_embeddertest.cpp b/fpdfsdk/src/fpdfformfill_embeddertest.cpp
index 6baad11531..56710b9f83 100644
--- a/fpdfsdk/src/fpdfformfill_embeddertest.cpp
+++ b/fpdfsdk/src/fpdfformfill_embeddertest.cpp
@@ -40,6 +40,18 @@ TEST_F(FPDFFormFillEmbeddertest, BUG_487928) {
   UnloadPage(page);
 }
 
+TEST_F(FPDFFormFillEmbeddertest, BUG_507316) {
+  EmbedderTestTimerHandlingDelegate delegate;
+  SetDelegate(&delegate);
+
+  EXPECT_TRUE(OpenDocument("testing/resources/bug_507316.pdf"));
+  FPDF_PAGE page = LoadAndCachePage(2);
+  EXPECT_NE(nullptr, page);
+  DoOpenActions();
+  delegate.AdvanceTime(4000);
+  UnloadPage(page);
+}
+
 TEST_F(FPDFFormFillEmbeddertest, BUG_514690) {
   EXPECT_TRUE(OpenDocument("testing/resources/hello_world.pdf"));
   FPDF_PAGE page = LoadPage(0);