On Thu, Nov 29, 2012 at 02:34:52PM -0500, Benjamin LaHaise wrote: > On Thu, Nov 29, 2012 at 11:29:25AM -0800, Kent Overstreet wrote: > > There's some kind of symmetry going on here, and if I'd been awake more > > in college I could probably say exactly why it works, but it does. > > I think the catch is that using only a 32 bit counter is something the > user could arbitrarily control the sum of all parts. I think a 64 bit > counter may be required to ensure no overflow occurs. Otherwise, an > overflow could result in a premature free when there are still 2^32 > objects active thanks to a malicious user (possible on systems with lots > of memory these days -- remote, but possible).
That's no different from regular atomic_t - but you're right, we should be using size_t for anything userspace can manipulate. Not gonna worry about it in this patch though because the refcount was an atomic_t before and userspace can only do one get per thread. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
