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Another approach to preventing stack buffer overflow exploitation is to enforce a memory policy on the stack memory region that disallows execution from the stack (W^X, "Write XOR Execute"). This means that in order to execute shellcode from the stack an attacker must either find a way to disable the execution protection from memory, or find a ...
If this overwrites adjacent data or executable code, this may result in erratic program behavior, including memory access errors, incorrect results, and crashes. Exploiting the behavior of a buffer overflow is a well-known security exploit. On many systems, the memory layout of a program, or the system as a whole, is well defined.
In computer programming, a weak reference is a reference that does not protect the referenced object from collection by a garbage collector, unlike a strong reference.An object referenced only by weak references – meaning "every chain of references that reaches the object includes at least one weak reference as a link" – is considered weakly reachable, and can be treated as unreachable and ...
A memory debugger is a debugger for finding software memory problems such as memory leaks and buffer overflows. These are due to bugs related to the allocation and deallocation of dynamic memory . Programs written in languages that have garbage collection , such as managed code , might also need memory debuggers, e.g. for memory leaks due to ...
A memory leak may also happen when an object is stored in memory but cannot be accessed by the running code (i.e. unreachable memory). [2] A memory leak has symptoms similar to a number of other problems and generally can only be diagnosed by a programmer with access to the program's source code.
Another frequent source of dangling pointers is a jumbled combination of malloc() and free() library calls: a pointer becomes dangling when the block of memory it points to is freed. As with the previous example one way to avoid this is to make sure to reset the pointer to null after freeing its reference—as demonstrated below.
This is a special case of violation of memory safety. Buffer over-reads can be triggered, as in the Heartbleed bug, by maliciously crafted inputs that are designed to exploit a lack of bounds checking to read parts of memory not intended to be accessible. They may also be caused by programming errors alone.
Instead, a phantom reference is a mechanism that allows the garbage collector to notify the program when the referenced object has become phantom reachable. An object is phantom reachable, if it still resides in memory and it is referenced by a phantom reference, but its finalizer has already executed.