On Wed, Oct 16, 2024 at 5:48 PM Jan Kara <jack@xxxxxxx> wrote: > > Hello Amir! > > On Thu 03-10-24 16:29:22, Amir Goldstein wrote: > > When working in "fd mode", fanotify_read() needs to open an fd > > from a dentry to report event->fd to userspace. > > > > Opening an fd from dentry can fail for several reasons. > > For example, when tasks are gone and we try to open their > > /proc files or we try to open a WRONLY file like in sysfs > > or when trying to open a file that was deleted on the > > remote network server. > > > > Add a new flag FAN_REPORT_FD_ERROR for fanotify_init(). > > For a group with FAN_REPORT_FD_ERROR, we will send the > > event with the error instead of the open fd, otherwise > > userspace may not get the error at all. > > > > The FAN_REPORT_FD_ERROR flag is not allowed for groups in "fid mode" > > which do not use open fd's as the object identifier. > > > > For ean overflow event, we report -EBADF to avoid confusing FAN_NOFD > > with -EPERM. Similarly for pidfd open errors we report either -ESRCH > > or the open error instead of FAN_NOPIDFD and FAN_EPIDFD. > > > > In any case, userspace will not know which file failed to > > open, so add a debug print for further investigation. > > > > Reported-by: Krishna Vivek Vitta <kvitta@xxxxxxxxxxxxx> > > Closes: https://lore.kernel.org/linux-fsdevel/SI2P153MB07182F3424619EDDD1F393EED46D2@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > > Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> > > I was mulling over this becase I wasn't quite happy with the result but I > could not clearly formulate my problems with the patch. So I've just sat > down and played with the code. Attached is what I've ended up with - please > have a look if it looks OK to you as well, it passes the LTP test you've > created. Functionally, I've just removed the check that FAN_REPORT_FD_ERROR > cannot be used in "fid mode" because when we decided to use the flag for > pidfd, it makes sense to combine it with "fid mode". I've also moved > EOPENSTALE special handling to a more logical place now. > Yeh this looks nicer. Thanks for the touch up. Amir.
