On Wed, May 09, 2012 at 05:28:54PM +0100, Al Viro wrote: > On Wed, May 09, 2012 at 06:23:30PM +0200, Sasha Levin wrote: > > On Wed, May 9, 2012 at 6:12 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > > On Wed, May 09, 2012 at 05:25:14PM +0200, Sasha Levin wrote: > > >> Hi all, > > >> > > >> I've started seeing the following warning while fuzzing inside a KVM guest with the latest -next: > > > ? ? ? ?It's not a realistic attack, fortunately, since you need root > > > to get past open_exec() on any of those... ?Wait. ?How _did_ you get > > > past open_exec(), anyway? ?MAY_EXEC is not supposed to be granted on > > > anything that has no exec bits at all and AFAICS none of those files > > > have them. > > > > You could chmod +x and run them, no? > > Can't. proc_setattr() will give you -EPERM and refuse to do anything > if you call it with ATTR_MODE in ->ia_valid. OTOH, you probably can do that on unrelated seq_file outside of per-process part of procfs. So, yes, one could get a warning like that if they, as root, would do e.g. chmod +x /proc/swaps attempt to execve() /proc/swaps cat /proc/self/environ and enjoy the hard-earned false positive (it's a different seq_file, so we have no deadlock). If that's _all_ that happened, I'm not particulary concerned; it's not pretty, but saying "thou shalt not grab ->cred_guard_mutex anywhere in ->read() on anything that has exec bits or might get one" is not too terrible. If that's something else, though, we might have a real problem... -- 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
