On Fri, 13 Jun 2014, Thomas Gleixner wrote: > On Thu, 12 Jun 2014, Darren Hart wrote: > > > On Wed, 2014-06-11 at 20:45 +0000, Thomas Gleixner wrote: > > > futex_lock_pi_atomic() is a maze of retry hoops and loops. > > > > > > Reduce it to simple and understandable states: > > > > Heh... well... > > > > With this patch applied (1-4 will not reproduce without 5), if userspace > > wrongly sets the uval to 0, the pi_state can end up being NULL for a > > subsequent requeue_pi operation: > > > > [ 10.426159] requeue: 00000000006022e0 to 00000000006022e4 > > [ 10.427737] this:ffff88013a637da8 > > [ 10.428749] waking:ffff88013a637da8 > > fut2 = 0 > > [ 10.429994] comparing requeue_pi_key > > [ 10.431034] prepare waiter to take the rt_mutex > > [ 10.432344] pi_state: (null) > > [ 10.433414] BUG: unable to handle kernel NULL pointer dereference at > > 0000000000000038 > > > > This occurs in the requeue loop, in the requeue_pi block at: > > > > atomic_inc(&pi_state->refcount); > > Hmm. Took me some time to reproduce. Digging into it now.
I'm a moron. Ran out of brown paperbags .... -- 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/
