Re: [RFC v2 PATCH] futex: extend set_robust_list to allow 2 locking ABIs at the same time.

* Zack Weinberg:

On Tue, Nov 5, 2019 at 9:28 AM Thomas Gleixner [off-list ref] wrote:

quoted

The real issue is that the robust list could be circular by incident or
malice and there is no way for the kernel to figure that out. That would
prevent the task from exiting and make it iterate over the list until
doomsday, i.e. a nice unpriviledged DoS.

Why can't the kernel use the standard tortoise-and-hare algorithm for
detecting circular linked lists here?

It's not guaranteed to terminate if the list is in shared memory.

Thanks,
Florian