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Heap pollution in Java can occur when type arguments and variables are not reified at run-time. As a result, different parameterized types are implemented by the same class or interface at run time. All invocations of a given generic type declaration share a single run-time implementation. This results in the possibility of heap pollution. [2]
The canonical heap overflow technique overwrites dynamic memory allocation linkage (such as malloc metadata) and uses the resulting pointer exchange to overwrite a program function pointer. For example, on older versions of Linux , two buffers allocated next to each other on the heap could result in the first buffer overwriting the second ...
Also, when implemented with the "shortest first" policy, the worst-case space complexity is instead bounded by O(log(n)). Heapsort has O(n) time when all elements are the same. Heapify takes O(n) time and then removing elements from the heap is O(1) time for each of the n elements. The run time grows to O(nlog(n)) if all elements must be distinct.
Executable space protection is an approach to buffer overflow protection that prevents execution of code on the stack or the heap. An attacker may use buffer overflows to insert arbitrary code into the memory of a program, but with executable space protection, any attempt to execute that code will cause an exception.
Garbage consumes heap memory, and thus one wishes to collect it (to minimize memory use, allow faster memory allocation, and prevent out-of-memory errors by reducing heap fragmentation and memory use). However, collecting garbage takes time and, if done manually, requires coding overhead.
Instead of separating the code from the data, another mitigation technique is to introduce randomization to the memory space of the executing program. Since the attacker needs to determine where executable code that can be used resides, either an executable payload is provided (with an executable stack) or one is constructed using code reuse ...
If the computer runs out of both memory and swap space, the OS might automatically reboot — or even worse hang. [ 15 ] Programs written in programming languages that use a garbage collector (e.g. Java ) are less prone to memory leaks, since memory that is no longer referenced will be freed up by the garbage collector.
Java does not support access to individual bytes, only objects which are 8-byte aligned by default. Because of this, the lowest 3 bits of a heap reference will always be 0. By lowering the resolution of 32-bit references to 8 byte blocks, the addressable space can be increased to 32 GB.