Am 05.05.2020 um 11:16 hat Alberto Garcia geschrieben: > On Tue 05 May 2020 10:54:12 AM CEST, Kevin Wolf wrote: > > But I think there is a more important problem with the test: It seems > > to pass even with old binaries that don't have the fix. Is this only > > on my system or do you get the same? > > With old binaries when qcow2_cluster_zeroize() is called it receives > bytes = (UINT64_MAX - 9216), however that number is then used to > calculate the number of affected clusters, so it's rounded up, wraps > around again and back to zero. There's no visible sign of the error, it > just happens to work fine. > > If there was a raw data file then we would try to write UINT64_MAX-9216 > bytes to it, but in this case there's no backing file allowed and > therefore the image is not zeroed, so qcow2_cluster_zeroize() never > happens. > > Why the test case then? There was a mistake with my first patch and > there it crashed (due to an assertion), that's why Eric thought it would > be a good idea to add a test case anyway, in case we have to change that > code in the future and we screw up.
Thanks for the explanation, this makes sense. I'll apply the patch now. Kevin
