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An accidental overflow may result in data corruption or unexpected behavior by any process that accesses the affected memory area. On operating systems without memory protection, this could be any process on the system. For example, a Microsoft JPEG GDI+ buffer overflow vulnerability could allow remote execution of code on the affected machine. [1]
The canonical heap overflow technique overwrites dynamic memory allocation linkage (such as malloc meta data) and uses the resulting pointer exchange to overwrite a program function pointer. Microsoft's GDI+ vulnerability in handling JPEGs is an example of the danger a heap overflow can present. [5]
Stack buffer overflow is a type of the more general programming malfunction known as buffer overflow (or buffer overrun). [1] Overfilling a buffer on the stack is more likely to derail program execution than overfilling a buffer on the heap because the stack contains the return addresses for all active function calls.
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.
A heap spray can be used to introduce a large amount of order to compensate for this and increase the chances of successful exploitation. Heap sprays take advantage of the fact that on most architectures and operating systems, the start location of large heap allocations is predictable and consecutive allocations are roughly sequential.
A code sanitizer is a programming tool that detects bugs in the form of undefined or suspicious behavior by a compiler inserting instrumentation code at runtime. The class of tools was first introduced by Google's AddressSanitizer (or ASan) of 2012, which uses directly mapped shadow memory to detect memory corruption such as buffer overflows or accesses to a dangling pointer (use-after-free).
For example, an addition may produce an arithmetic overflow (it does not fulfill its contract of computing a good approximation to the mathematical sum); or a routine may fail to meet its postcondition. Exception: an abnormal event occurring during the execution of a routine (that routine is the "recipient" of the exception) during its execution.
In the example, 1 & 2 were the first to enter the circular buffer, they are the first to be removed, leaving 3 inside of the buffer. If the buffer has 7 elements, then it is completely full: A property of the circular buffer is that when it is full and a subsequent write is performed, then it starts overwriting the oldest data.