On Sat, May 24, 2008 at 01:44:32AM +0200, Nick Piggin wrote: > On Fri, May 23, 2008 at 01:31:12PM +0100, apw@xxxxxxxxxxxx wrote: > > On Fri, May 23, 2008 at 04:27:33AM +0200, Nick Piggin wrote: > > > > [...] > > > > I did wonder if we could also check _PAGE_BIT_USER bit as by my reading > > > > that would only ever be set on user pages, and by rejecting pages without > > > > that set we could prevent any kernel pages being returned basically > > > > for free. > > > > > > I still do want the access_ok check to avoid any possible issues with > > > kernel page table modifications... but checking for the user bit would > > > be another good sanity check, good idea. > > > > Definatly not advocating removing any checks at all. Just thinking the > > addition is one more safety net should any one of the checks be flawed. > > Security being a pig to prove at the best of times. > > It isn't a bad idea at all. I'll see what I can do. Oh, hmm, I was already checking the _PAGE_USER bit anyway ;) -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
