Contents
Can the heap overflow into the stack?
Heap overflows are exploitable in a different manner to that of stack-based overflows. Memory on the heap is dynamically allocated at runtime and typically contains program data.
What are the differences between stack and heap based buffer overflows?
Stack overflows corrupt memory on the stack. This means that values of local variables, function arguments, and return addresses are affected. Whereas heap overflows refer to overflows that corrupt memory located on the heap. Global variables and other program data are affected.
Why buffer overflow attack malicious code is pushed into stack?
Accessing of values in the stack is very fast. Explanation: Malicious code can be pushed into the stack during the buffer-overflow attack. The overflow can be used to overwrite the return pointer so that the control-flow switches to the malicious code.
Can the heap overflow?
Heap handles the dynamic storage of the data. One has to manually allocate and de-allocate the memory in heap storage using the malloc() and calloc() functions. When the memory management process is neglected, a heap overflow occurs which can affect the entire system code drastically.
Why is the stack more susceptible to buffer overflows than the heap?
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. A stack buffer overflow can be caused deliberately as part of an attack known as stack smashing.
Why are there buffer overflows on the heap?
In old or bad heap implementations that might be heap metadata that can give you e.g. the power to write stuff into memory (which you could use to overwrite a function pointer).
How can a buffer overflow overwrite content above the variable?
So if the stack grows downwards, that means that the return address is above the variable’s reserved space. When that variable is now overflowed, shouldn’t it overwrite memory below instead of above? tl;dr: If the stack grows downwards, how can a buffer overflow overwrite content above the variable?
Do you use the stack or the heap?
Allocated buffers may not use the stack, but the heap. This depends on how they are allocated and what the compiler though would be better/faster/etc. A stack overflow does indeed override memory below, which may have been assigned to another (prior) call or ultimately the heap.
What are the different types of buffer overflows?
Stack-based buffer overflows are more common, and leverage stack memory that only exists during the execution time of a function. Heap-based attacks are harder to carry out and involve flooding the memory space allocated for a program beyond memory used for current runtime operations.