On Thu, Aug 31, 2017 at 6:58 AM, Mike Galbraith [off-list ref] wrote:

gdb) list *in6_dev_get+0x10
0xffffffff8166d3d0 is in in6_dev_get (./include/net/addrconf.h:318).
313     {
314             struct inet6_dev *idev;
315
316             rcu_read_lock();
317             idev = rcu_dereference(dev->ip6_ptr);
318             if (idev)
319                     refcount_inc(&idev->refcnt);
320             rcu_read_unlock();
321             return idev;
322

And this is a completely different refcount from the other that
tripped. This one is quite simple, too, though I see it uses
refcount_dec(), which is a path to saturation. I've sent a patch to
try to clarify this further...

-Kees

-- 
Kees Cook
Pixel Security