[compiler-rt] 18959a6 - [hwasan] Fix missing synchronization in AllocThread.

[Evgenii Stepanov via llvm-commits]

Author: Evgenii Stepanov
Date: 2021-05-05T11:57:18-07:00
New Revision: 18959a6a094c6469fc2fd5cc167fda7cbe3f163b

URL: https://github.com/llvm/llvm-project/commit/18959a6a094c6469fc2fd5cc167fda7cbe3f163b
DIFF: https://github.com/llvm/llvm-project/commit/18959a6a094c6469fc2fd5cc167fda7cbe3f163b.diff

LOG: [hwasan] Fix missing synchronization in AllocThread.

The problem was introduced in D100348.

It's really hard to trigger the bug in a stress test - the race is just too
narrow - but the new checks in Thread::Init should at least provide usable
diagnostic if the problem ever returns.

Differential Revision: https://reviews.llvm.org/D101881

Added: 
    

Modified: 
    compiler-rt/lib/hwasan/hwasan_thread.cpp
    compiler-rt/lib/hwasan/hwasan_thread_list.h

Removed: 
    


################################################################################
diff  --git a/compiler-rt/lib/hwasan/hwasan_thread.cpp b/compiler-rt/lib/hwasan/hwasan_thread.cpp
index c1f0e013b49f5..bb4d56abed0a7 100644
--- a/compiler-rt/lib/hwasan/hwasan_thread.cpp
+++ b/compiler-rt/lib/hwasan/hwasan_thread.cpp
@@ -35,6 +35,10 @@ void Thread::InitRandomState() {
 }
 
 void Thread::Init(uptr stack_buffer_start, uptr stack_buffer_size) {
+  CHECK_EQ(0, unique_id_);  // try to catch bad stack reuse
+  CHECK_EQ(0, stack_top_);
+  CHECK_EQ(0, stack_bottom_);
+
   static u64 unique_id;
   unique_id_ = unique_id++;
   if (auto sz = flags()->heap_history_size)

diff  --git a/compiler-rt/lib/hwasan/hwasan_thread_list.h b/compiler-rt/lib/hwasan/hwasan_thread_list.h
index 3b89bad59cc30..11c586314ce75 100644
--- a/compiler-rt/lib/hwasan/hwasan_thread_list.h
+++ b/compiler-rt/lib/hwasan/hwasan_thread_list.h
@@ -173,6 +173,7 @@ class HwasanThreadList {
 
  private:
   Thread *AllocThread() {
+    SpinMutexLock l(&free_space_mutex_);
     uptr align = ring_buffer_size_ * 2;
     CHECK(IsAligned(free_space_, align));
     Thread *t = (Thread *)(free_space_ + ring_buffer_size_);
@@ -181,6 +182,7 @@ class HwasanThreadList {
     return t;
   }
 
+  SpinMutex free_space_mutex_;
   uptr free_space_;
   uptr free_space_end_;
   uptr ring_buffer_size_;