On 6/15/20 1:24 AM, Miklos Szeredi wrote: > On Sat, Jun 13, 2020 at 8:53 AM Amir Goldstein <amir73il@xxxxxxxxx> wrote: > >>> I also looked at normal filesystem lower and hugetlbfs upper. Yes, overlayfs >>> allows this. This is somewhat 'interesting' as write() is not supported in >>> hugetlbfs. Writing to files in the overlay actually ended up writing to >>> files in the lower filesystem. That seems wrong, but overlayfs is new to me. > > Yes, this very definitely should not happen. > >> I am not sure how that happened, but I think that ovl_open_realfile() >> needs to fixup f_mode flags FMODE_CAN_WRITE | FMODE_CAN_READ >> after open_with_fake_path(). > > Okay, but how did the write actually get to the lower layer? > > I failed to reproduce this. Mike, how did you trigger this? My apologies!!! I reviewed my testing and found that it was incorrectly writing to the lower filesystem. Writing to any file in the union will fail. -- Mike Kravetz
