src: fix uninitialized memory dereference

bnoordhuis · bnoordhuis · commit 78e38f59ad9f · 2014-10-28T12:42:14.000+01:00
The elements of the heap-allocated TaskQueue::ring_ array in src/node_v8_platform.cc were compared against without being initialized first. Fixes node-forward/node#33. PR-URL: node-forward/node#34 Reviewed-By: Fedor Indutny <fedor@indutny.com>
diff --git a/src/node_v8_platform.cc b/src/node_v8_platform.cc
@@ -98,12 +98,9 @@ void Platform::WorkerBody(void* arg) {
 TaskQueue::TaskQueue() {
   int err;
 
-  static_assert(kRingSize == (kRingSize & (~(kRingSize - 1))),
-                "kRingSize is not a power of two");
+  for (size_t i = 0; i < ARRAY_SIZE(ring_); i += 1)
+    ring_[i] = nullptr;
 
-  size_ = kRingSize;
-  ring_ = new Task*[size_];
-  mask_ = size_ - 1;
   read_off_ = 0;
   write_off_ = 0;
 
@@ -120,9 +117,6 @@ TaskQueue::TaskQueue() {
 
 TaskQueue::~TaskQueue() {
   CHECK_EQ(read_off_, write_off_);
-
-  delete[] ring_;
-  ring_ = nullptr;
   uv_sem_destroy(&sem_);
   uv_cond_destroy(&cond_);
   uv_mutex_destroy(&mutex_);
@@ -138,7 +132,7 @@ void TaskQueue::Push(Task* task) {
 
   ring_[write_off_] = task;
   write_off_++;
-  write_off_ &= mask_;
+  write_off_ &= kRingMask;
   uv_mutex_unlock(&mutex_);
 
   uv_sem_post(&sem_);
@@ -154,7 +148,7 @@ Task* TaskQueue::Shift() {
   uv_cond_signal(&cond_);
 
   read_off_++;
-  read_off_ &= mask_;
+  read_off_ &= kRingMask;
   uv_mutex_unlock(&mutex_);
 
   return task;
diff --git a/src/node_v8_platform.h b/src/node_v8_platform.h
@@ -37,15 +37,17 @@ class TaskQueue {
 
  private:
   static const unsigned int kRingSize = 1024;
+  static const unsigned int kRingMask = kRingSize - 1;
+
+  static_assert(kRingSize == (kRingSize & ~kRingMask),
+                "kRingSize is not a power of two");
 
   uv_sem_t sem_;
   uv_cond_t cond_;
   uv_mutex_t mutex_;
-  v8::Task** ring_;
-  unsigned int size_;
-  unsigned int mask_;
   unsigned int read_off_;
   unsigned int write_off_;
+  v8::Task* ring_[kRingSize];
 };
 
 class Platform : public v8::Platform {
