Hello John and Matthew, Thanks a lot for your further explanation of this issue! It really helps me have a deeper understanding of the testing interface used in the kernel. Best, Chenyuan On Fri, Jan 26, 2024 at 1:09 PM John Hubbard <jhubbard@xxxxxxxxxx> wrote: > > On 1/26/24 10:34, Matthew Wilcox wrote: > > On Fri, Jan 26, 2024 at 11:31:26AM -0600, Chenyuan Yang wrote: > >> In this context, I would like to seek your valued opinion. Do you > >> believe it would be more prudent to avoid fuzz testing the > >> `gup_test_ioctl`, or are the warnings in `gup_test_ioctl` an > >> anticipated outcome? > > > > It seems like a waste of time. Debian certainly disables it, so > > unless you can find a distro who enables it, I wouldn't bother. > > +1000! The purpose of gup_test_ioctl is to provide a way to invoke, > from user space, direct testing of some kernel interfaces that are > not actually exposed to user space for production systems. > > Fuzzing this interface is exactly what you should never do. :) > > > > >> It seems that `gup_test_ioctl` can indeed be exposed in the kernel by > >> accessing /sys/kernel/debug/gup_test. > > That's a debug interface. > > > > > If someone wants to fix these things, they can, but it just doesn't > > seem worth doing. Part of the art of fuzz testing is finding things > > that are worth testing. > > I'll go just slightly further, even: some conceivable "fixes" could end > up hurting test coverage. Without providing any real benefit. > > > thanks, > -- > John Hubbard > NVIDIA > >
