(private noaw) On Mon, Feb 02, 2015 at 04:11:59PM +0100, Peter Zijlstra wrote: > On Mon, Feb 02, 2015 at 03:05:15PM +0100, Oleg Nesterov wrote: > > > First of all, why exactly do we need this mm/PF_KTHREAD check added by > > f0d71b3dcb8332f7971 ? Of course, it is simply wrong to declare a random > > kernel thread to be the owner as the changelog says. But why kthread is > > worse than a random user-space task, say, /sbin/init? > > As the changelog says, we _should_ equally disallow other userspace > tasks that do not share the futex value with us, its just that at the > time we could not come up with a sensible (and cheap) way of testing for > this. > > > IIUC, the fact that we can abuse ->pi_state_list is not that bad, no matter > > if this (k)thread will exit or not. AFAICS, the only problem is that we can > > boost the prio of this thread. Or I missed another problem? > > No that's it.
Prio leaks allow (local) DoS attacks. It allows an unpriv user to gain FIFO and burn silly amounts of cycles. We should really plug that hole entirely. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
