Re: VFS event hooks

Pavel Machek (pavel@bug.ucw.cz)
Wed, 30 Jun 1999 22:17:34 +0200


Hi!

> > > It patches against 2.3.5 and 2.3.8. Currently only ext2fs directories
> > > support inode change events, but it gives you the idea. I considered
> > > hacking do_select() and do_poll() to call vfs_poll() directly, but
> > > that would have introduced more tests to the critical path.
> >
> > Hmm -- does not this open DoS attack? What about users taking poll at
> > _many_ directories and eating nonswappable ram this way? You seem to
> > need to remember what last poll did, so something like
> >
> > poll("/usr")
> > poll("/usr/src")
> > poll("/usr/X11")
>
> But it doesn't work this way. It looks like this:
> fd1 = open ("/usr");
> fd2 = open ("/usr/src");
> fd3 = open ("/usr/X11");
> poll (fd1...fd3);
>
> So there's no denial of service. You may as well argue that open() is
> a potential denial of service.

Oops, sorry. He is right and I'm wrong. Actually, this looks like good
idea.

Pavel

-- 
I'm really pavel@ucw.cz. Look at http://195.113.31.123/~pavel.  Pavel
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