[hwasan] Fix data race between ReleaseThread() and VisitAllLiveThreads()

[Enna1]

Summary

Data race scenario:

Thread 1                                | Thread 2
ReportTagMismatch()                     |
Call VisitAllLiveThreads() to scan all  |
threads' ring buffers to find           |
if it's a heap-use-after-free.          |
Lock live_list_mutex_                   |
                                        | Thread 2 exit
                                        | ReleaseThread() calls Thread::Destroy() for Thread 2,
                                        | which frees heap alloctions ring buffer
                                        | RemoveThreadFromLiveList() tries to take live_list_mutex_ again
Iterate the heap alloctions ring buffer |
of Thread 2, which is already freed     |

[Enna1]

We encountered a crash due to this data race during the process of enabling hwasan for our server-side applications on AArch64/Linux. With this change, the crash will be fixed.

But can't figure out how to write a test case for this, still trying.

[vitalybuka]

Would be nice to have a simple reproducer as a test, but LGTM as-is if that's hard.

compiler-rt/lib/hwasan/hwasan_thread_list.h

for (Thread *&t2 : live_list_)
         live_list_.pop_back();
         return;
       }
     CHECK(0 && "thread not found in live list");
   }
 
   void ReleaseThread(Thread *t) SANITIZER_EXCLUDES(free_list_mutex_) {
     RemoveThreadStats(t);
+    RemoveThreadFromLiveList(t);
     t->Destroy();
     DontNeedThread(t);
-    RemoveThreadFromLiveList(t);
     SpinMutexLock l(&free_list_mutex_);
     free_list_.push_back(t);
   }
 
   Thread *GetThreadByBufferAddress(uptr p) {
     return (Thread *)(RoundDownTo(p, ring_buffer_size_ * 2) +
                       ring_buffer_size_);
   }