The task struct has a lock (itk_lock_data, taken via the itk_lock macros) which is supposed to
protect the task->itk_* ports.
The host_self_trap mach trap accesses task->itk_host without taking this lock leading to a use-after-free
given the following interleaving of execution:
Thread A: host_self_trap:
read current_task()->itk_host // Thread A reads itk_host
Thread B: task_set_special_port:
*whichp = port; // Thread B replaces itk_host with eg MACH_PORT_NULL
itk_unlock(task);
if (IP_VALID(old))
ipc_port_release_send(old); // Thread B drops last ref on itk_host
Thread A: host_self_trap:
passes the port to ipc_port_copy_send // uses the free'd port
host_self_trap should use one of the canonical accessors for the task's host port, not just directly read it.
PoC tested on MacOS 10.12.1
