On Sun, 3 May 2009, Al Viro wrote:
> On Mon, Apr 27, 2009 at 02:33:34PM -0400, Gregory Haskins wrote:
> > + /* We re-use eventfd for irqfd */
> > + fd = sys_eventfd2(0, 0);
> > + if (fd < 0) {
> > + ret = fd;
> > + goto fail;
> > + }
> > +
> > + /* We maintain a reference to eventfd for the irqfd lifetime */
> > + file = eventfd_fget(fd);
> > + if (IS_ERR(file)) {
> > + ret = PTR_ERR(file);
> > + goto fail;
> > + }
> > +
> > + irqfd->file = file;
>
> This is just plain wrong. You have no promise whatsoever that caller of
> that sucker won't race with e.g. dup2(). IOW, you can't assume that
> file will be of the expected kind.
The eventfd_fget() checks for the file_operations pointer, before
returning the file*, and fails if the fd in not an eventfd. Or you have
other concerns?
- Davide
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