src/hotspot/os/linux/os_linux.cpp

@@ -3104,11 +3104,14 @@
 }
 
 bool os::committed_in_range(address start, size_t size, address& committed_start, size_t& committed_size) {
   int mincore_return_value;
   const size_t stripe = 1024;  // query this many pages each time
-  unsigned char vec[stripe];
+  unsigned char vec[stripe + 1];
+  // set a guard
+  vec[stripe] = 'X';
+
   const size_t page_sz = os::vm_page_size();
   size_t pages = size / page_sz;
 
   assert(is_aligned(start, page_sz), "Start address must be page aligned");
   assert(is_aligned(size, page_sz), "Size must be page aligned");

@@ -3116,11 +3119,13 @@
   committed_start = NULL;
 
   int loops = (pages + stripe - 1) / stripe;
   int committed_pages = 0;
   address loop_base = start;
-  for (int index = 0; index < loops; index ++) {
+  bool found_range = false;
+
+  for (int index = 0; index < loops && !found_range; index ++) {
     assert(pages > 0, "Nothing to do");
     int pages_to_query = (pages >= stripe) ? stripe : pages;
     pages -= pages_to_query;
 
     // Get stable read

@@ -3131,16 +3136,18 @@
     // Bailout and return as not committed for now.
     if (mincore_return_value == -1 && errno == ENOMEM) {
       return false;
     }
 
+    assert(vec[stripe] == 'X', "overflow guard");
     assert(mincore_return_value == 0, "Range must be valid");
     // Process this stripe
     for (int vecIdx = 0; vecIdx < pages_to_query; vecIdx ++) {
       if ((vec[vecIdx] & 0x01) == 0) { // not committed
         // End of current contiguous region
         if (committed_start != NULL) {
+          found_range = true;
           break;
         }
       } else { // committed
         // Start of region
         if (committed_start == NULL) {