[ubuntu-hardened] Add overflow protection to kref

[Greg KH]

On Thu, Feb 16, 2012 at 09:48:38PM -0500, David Windsor wrote:
> <snip>
> 
> >>
> >> I have yet to see a patch, so why are we arguing about this?  :)
> >>
> >> Again, I don't know of any kref overflows that have ever happened, so
> >> trying to "protect" this type of thing, seems odd to me.
> >
> > Well, I think the issue was to protect counting things (which seems to
> > be what PaX was after originally), and that kref seemed like the place
> > to put it. I'll let David take it further.
> >
> 
> Patches are forthcoming that will first introduce overflow protection
> to kref.  Once that's in place, I'll move a few refcount users from
> atomic_t to kref as a reference for other subsystems;

I'd like to see some more users first, as I don't see how the current
users could ever overflow an atomic_t, so any changes to prevent this
will be kind of pointless, right?

So feel free to send all of these changes together.

thanks,

greg k-h