Re: [KVM PATCH v3 2/2] kvm: add support for irqfd via eventfd-notificationinterface

[Davide Libenzi]

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


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/