Kernel: Fix ASSERTION failed in join_thread syscall

set_interrupted_by_death was never called whenever a thread that had
a joiner died, so the joiner remained with the joinee pointer there,
resulting in an assertion fail in JoinBlocker: m_joinee pointed to
a freed task, filled with garbage.

Thread::current->m_joinee may not be valid after the unblock

Properly return the joinee exit value to the joiner thread.

Kernel/Process.cpp

@@ -3844,10 +3844,14 @@ int Process::sys$join_thread(int tid, void** exit_value)
  if (result == Thread::BlockResult::InterruptedByDeath) {
  // NOTE: This cleans things up so that Thread::finalize() won't
  // get confused about a missing joiner when finalizing the joinee.
- InterruptDisabler disabler;
- Thread::current->m_joinee->m_joiner = nullptr;
- Thread::current->m_joinee = nullptr;
- return 0;
+ InterruptDisabler disabler_t;
+
+ if (Thread::current->m_joinee) {
+ Thread::current->m_joinee->m_joiner = nullptr;
+ Thread::current->m_joinee = nullptr;
+ }
+
+ break;
  }
  }
 

Kernel/Thread.cpp

@@ -300,6 +300,7 @@ void Thread::finalize()
  if (m_joiner) {
  ASSERT(m_joiner->m_joinee == this);
  static_cast<JoinBlocker*>(m_joiner->m_blocker)->set_joinee_exit_value(m_exit_value);
+ static_cast<JoinBlocker*>(m_joiner->m_blocker)->set_interrupted_by_death();
  m_joiner->m_joinee = nullptr;
  // NOTE: We clear the joiner pointer here as well, to be tidy.
  m_joiner = nullptr;