MiddleDebuggingCommonNot answered yet

What happens if you write more data than you allocated (buffer overflow)?

This function copies a name into a fixed-size buffer. With a long input the program corrupts memory, crashes, or — worse — silently keeps running.

void store(const char* name) {
    char buf[16];
    std::strcpy(buf, name);
    std::cout << buf << '\n';
}

Identify the bug and explain the cause.

Writing past the allocated region corrupts adjacent memory: on the stack this overwrites the return address (stack smashing); on the heap it corrupts allocator metadata. Detect with AddressSanitizer, Valgrind, or stack canaries.

✗Using C-style strcpy/gets without size checks — these functions are the most common source of stack buffer overflows
✗Allocating n bytes but writing n+1 (null terminator) — classic off-by-one in string handling
✗Thinking std::string and std::vector prevent all overflows — incorrect bounds in manual indexing (operator[]) still overflow

→What is ASLR and how does it make buffer overflow exploits harder but not impossible?
→How do stack canaries detect stack buffer overflows?

Open topic in roadmap →

MiddleDebuggingCommonNot answered yet

What happens if you write more data than you allocated (buffer overflow)?

This function copies a name into a fixed-size buffer. With a long input the program corrupts memory, crashes, or — worse — silently keeps running.

void store(const char* name) {
    char buf[16];
    std::strcpy(buf, name);
    std::cout << buf << '\n';
}

Identify the bug and explain the cause.

✗Using C-style strcpy/gets without size checks — these functions are the most common source of stack buffer overflows
✗Allocating n bytes but writing n+1 (null terminator) — classic off-by-one in string handling
✗Thinking std::string and std::vector prevent all overflows — incorrect bounds in manual indexing (operator[]) still overflow

→What is ASLR and how does it make buffer overflow exploits harder but not impossible?
→How do stack canaries detect stack buffer overflows?

Open topic in roadmap →