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Avoid complex flow constructs, such as goto and recursion. All loops must have fixed bounds. This prevents runaway code. Avoid heap memory allocation. Restrict functions to a single printed page. Use a minimum of two runtime assertions per function. Restrict the scope of data to the smallest possible.
Memory errors were first considered in the context of resource management (computing) and time-sharing systems, in an effort to avoid problems such as fork bombs. [4] Developments were mostly theoretical until the Morris worm , which exploited a buffer overflow in fingerd . [ 5 ]
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 ...
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.
Canaries or canary words or stack cookies are known values that are placed between a buffer and control data on the stack to monitor buffer overflows. When the buffer overflows, the first data to be corrupted will usually be the canary, and a failed verification of the canary data will therefore alert of an overflow, which can then be handled, for example, by invalidating the corrupted data.
Illustration of the table-heap compaction algorithm. Objects that the marking phase has determined to be reachable (live) are colored, free space is blank. A table-based algorithm was first described by Haddon and Waite in 1967. [1] It preserves the relative placement of the live objects in the heap, and requires only a constant amount of overhead.
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]
A related concept is the "space leak", which is when a program consumes excessive memory but does eventually release it. [ 3 ] Because they can exhaust available system memory as an application runs, memory leaks are often the cause of or a contributing factor to software aging .