ole32: Do not crash in WriteClassStg if passed NULL pointer.

dlls/ole32/storage32.c

@@ -6281,6 +6281,9 @@ HRESULT WINAPI WriteClassStg(IStorage* pStg, REFCLSID rclsid)
   if(!pStg)
     return E_INVALIDARG;
 
+  if(!rclsid)
+    return STG_E_INVALIDPOINTER;
+
   hRes = IStorage_SetClass(pStg, rclsid);
 
   return hRes;

dlls/ole32/tests/storage32.c

@@ -803,6 +803,56 @@ static void test_storage_refcount(void)
     DeleteFileW(filename);
 }
 
+static void test_writeclassstg(void)
+{
+    static const WCHAR szPrefix[] = { 's','t','g',0 };
+    static const WCHAR szDot[] = { '.',0 };
+    WCHAR filename[MAX_PATH];
+    IStorage *stg = NULL;
+    HRESULT r;
+    CLSID temp_cls;
+
+    if(!GetTempFileNameW(szDot, szPrefix, 0, filename))
+        return;
+
+    DeleteFileW(filename);
+
+    /* create the file */
+    r = StgCreateDocfile( filename, STGM_CREATE | STGM_SHARE_EXCLUSIVE |
+                            STGM_READWRITE, 0, &stg);
+    ok(r==S_OK, "StgCreateDocfile failed\n");
+
+    r = ReadClassStg( NULL, NULL );
+    ok(r == E_INVALIDARG, "ReadClassStg should return E_INVALIDARG instead of 0x%08X\n", r);
+
+    r = ReadClassStg( stg, NULL );
+    ok(r == E_INVALIDARG, "ReadClassStg should return E_INVALIDARG instead of 0x%08X\n", r);
+
+    temp_cls.Data1 = 0xdeadbeef;
+    r = ReadClassStg( stg, &temp_cls );
+    ok(r == S_OK, "ReadClassStg failed with 0x%08X\n", r);
+
+    ok(IsEqualCLSID(&temp_cls, &CLSID_NULL), "ReadClassStg returned wrong clsid\n");
+
+    r = WriteClassStg( NULL, NULL );
+    ok(r == E_INVALIDARG, "WriteClassStg should return E_INVALIDARG instead of 0x%08X\n", r);
+
+    r = WriteClassStg( stg, NULL );
+    ok(r == STG_E_INVALIDPOINTER, "WriteClassStg should return STG_E_INVALIDPOINTER instead of 0x%08X\n", r);
+
+    r = WriteClassStg( stg, &test_stg_cls );
+    ok( r == S_OK, "WriteClassStg failed with 0x%08X\n", r);
+
+    r = ReadClassStg( stg, &temp_cls );
+    ok( r == S_OK, "ReadClassStg failed with 0x%08X\n", r);
+    ok(IsEqualCLSID(&temp_cls, &test_stg_cls), "ReadClassStg returned wrong clsid\n");
+
+    r = IStorage_Release( stg );
+    ok (r == 0, "storage not released\n");
+
+    DeleteFileW(filename);
+}
+
 static void test_streamenum(void)
 {
     static const WCHAR szPrefix[] = { 's','t','g',0 };
@@ -1229,4 +1279,5 @@ START_TEST(storage32)
     test_transact();
     test_ReadClassStm();
     test_access();
+    test_writeclassstg();
 }