ole32: Make sure StgIsStorageILockBytes tests real data.

dlls/ole32/storage32.c

@@ -7846,15 +7846,16 @@ HRESULT WINAPI StgSetTimes(OLECHAR const *str, FILETIME const *pctime,
  */
 HRESULT WINAPI StgIsStorageILockBytes(ILockBytes *plkbyt)
 {
-  BYTE sig[8];
+  BYTE sig[sizeof(STORAGE_magic)];
   ULARGE_INTEGER offset;
+  ULONG read = 0;
 
   offset.u.HighPart = 0;
   offset.u.LowPart  = 0;
 
-  ILockBytes_ReadAt(plkbyt, offset, sig, sizeof(sig), NULL);
+  ILockBytes_ReadAt(plkbyt, offset, sig, sizeof(sig), &read);
 
-  if (memcmp(sig, STORAGE_magic, sizeof(STORAGE_magic)) == 0)
+  if (read == sizeof(sig) && memcmp(sig, STORAGE_magic, sizeof(sig)) == 0)
     return S_OK;
 
   return S_FALSE;

dlls/ole32/tests/storage32.c

@@ -66,6 +66,9 @@ static void test_hglobal_storage_stat(void)
     r = CreateILockBytesOnHGlobal( NULL, TRUE, &ilb );
     ok( r == S_OK, "CreateILockBytesOnHGlobal failed\n");
 
+    r = StgIsStorageILockBytes( ilb );
+    ok( r == S_FALSE, "StgIsStorageILockBytes should have failed\n");
+
     mode = STGM_CREATE|STGM_SHARE_EXCLUSIVE|STGM_READWRITE;/*0x1012*/
     r = StgCreateDocfileOnILockBytes( ilb, mode, 0,  &stg );
     ok( r == S_OK, "StgCreateDocfileOnILockBytes failed\n");
@@ -73,6 +76,9 @@ static void test_hglobal_storage_stat(void)
     r = WriteClassStg( stg, &test_stg_cls );
     ok( r == S_OK, "WriteClassStg failed\n");
 
+    r = StgIsStorageILockBytes( ilb );
+    ok( r == S_OK, "StgIsStorageILockBytes failed\n");
+
     memset( &stat, 0, sizeof stat );
     r = IStorage_Stat( stg, &stat, 0 );