Re: tip -ENOBOOT - bisected to locking/refcounts, x86/asm: Implement fast refcount overflow protection

[Kees Cook]

On Thu, Aug 31, 2017 at 6:58 AM, Mike Galbraith <efault@xxxxxx> 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