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  1. JDK
  2. JDK-4039957

cbConstantPool allocated once; but deallocated twice -- heap corruption

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    • b01
    • generic
    • generic
    • Not verified

    Description

      > We think we found a problem in the JVM where memory gets allocated once but
      > deallocated twice. The problem showed up when we ran some of the JCK
      > vm.classfmt.classfile tests.
      >
      > The problem is in classloader.c. Memory for cbConstantPool(cb) gets allocated
      > once, and deallocated twice.
      >
      >
      > THE ALLOCATION
      > LoadClassFromFile() calls
      > createInternalClass() calls
      > createInternalClass0() calls
      > LoadConstantPool()
      > /* allocate constant_pool memory from 'context' heap */
      > constant_pool = (cp_item_type *)
      > allocNBytes(context, nconstants * sizeof(cp_item_type));
      > cbConstantPool(cb) = constant_pool;
      >
      >
      > THE FIRST DEALLOCATION
      > createInternalClass() calls freeBuffers if it is longjmp-ed to
      > as a result of an error being detected:
      > if (setjmp(context->jump_buffer)) {
      > /* We've gotten an error of some sort */
      > freeBuffers(context);
      > return FALSE;
      > }
      >
      > freeBuffers() deletes all the 'context' memory, including the
      > memory allocated by LoadConstantPool() for cbConstantPool(cb)
      >
      >
      > THE SECOND (AND ERRONEOUS) DEALLOCATION
      > LoadClassFromFile() detects the error returned by createInternalClass()
      > It then calls FreeClass() which illegaly frees cbConstantPool(cb)

      The above description is based on a 1.1 VM - but this still appears to be
      an issue in 1.1.1 even though cbConstantPool(cb) is not assigned a value
      until the end of the LoadConstantPool() routine.

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            sliangsunw Sheng Liang (Inactive)
            duke J. Duke
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