libv8 (2.2.24-6) issue3338001_1_2.diff

Summary

 src/cpu-profiler.cc |   15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

    
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Patch contents

Index: src/cpu-profiler.cc
===================================================================
--- a/src/cpu-profiler.cc	(revision 5392)
+++ b/src/cpu-profiler.cc	(working copy)
@@ -235,8 +235,19 @@
     const TickSampleEventRecord* rec =
         TickSampleEventRecord::cast(ticks_buffer_.StartDequeue());
     if (rec == NULL) return !ticks_from_vm_buffer_.IsEmpty();
-    if (rec->order == dequeue_order) {
-      generator_->RecordTickSample(rec->sample);
+    // Make a local copy of tick sample record to ensure that it won't
+    // be modified as we are processing it. This is possible as the
+    // sampler writes w/o any sync to the queue, so if the processor
+    // will get far behind, a record may be modified right under its
+    // feet.
+    TickSampleEventRecord record = *rec;
+    if (record.order == dequeue_order) {
+      // A paranoid check to make sure that we don't get a memory overrun
+      // in case of frames_count having a wild value.
+      if (record.sample.frames_count < 0
+          || record.sample.frames_count >= TickSample::kMaxFramesCount)
+        record.sample.frames_count = 0;
+      generator_->RecordTickSample(record.sample);
       ticks_buffer_.FinishDequeue();
     } else {
       return true;