Kent Overstreet <koverstreet@xxxxxxxxxx> writes: > 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. The regular atomic_t is limited in ways that you are not. See my original mail. -Andi -- ak@xxxxxxxxxxxxxxx -- Speaking for myself only -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
