bpo-34770: Fix a possible null pointer dereference in pyshellext.cpp (G…

…H-9497) The GlobalLock() call in UpdateDropDescription() was not checked for failure. https://bugs.python.org/issue34770 (cherry picked from commit f6c8007) Co-authored-by: Zackery Spytz <zspytz@gmail.com>
python · Sep 25, 2018 · db23206 · db23206
1 parent bbdf872
commit db23206
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diff --git a/Misc/NEWS.d/next/Windows/2018-09-22-11-02-35.bpo-34770.4lEUOd.rst b/Misc/NEWS.d/next/Windows/2018-09-22-11-02-35.bpo-34770.4lEUOd.rst
@@ -0,0 +1 @@
+Fix a possible null pointer dereference in pyshellext.cpp.
diff --git a/PC/pyshellext.cpp b/PC/pyshellext.cpp
@@ -172,6 +172,11 @@ class PyShellExt : public RuntimeClass<
             return E_FAIL;
         }
         auto dd = (DROPDESCRIPTION*)GlobalLock(medium.hGlobal);
+        if (!dd) {
+            OutputDebugString(L"PyShellExt::UpdateDropDescription - failed to lock DROPDESCRIPTION hGlobal");
+            ReleaseStgMedium(&medium);
+            return E_FAIL;
+        }
         StringCchCopy(dd->szMessage, sizeof(dd->szMessage) / sizeof(dd->szMessage[0]), DRAG_MESSAGE);
         StringCchCopy(dd->szInsert, sizeof(dd->szInsert) / sizeof(dd->szInsert[0]), PathFindFileNameW(target));
         dd->type = DROPIMAGE_MOVE;