Overflow error definition
An overflow error occurs when a computer operation produces a result that falls outside the permissible range of the respective data type. It happens because computers use a fixed number of bits (binary digits) to store a value. When an operation results in a value that cannot be represented within the allocated number of bits, it leads to an overflow error.
See also: integer overflow, buffer overflow attack, input validation attack
Overflow error types
- Arithmetic overflow. This occurs when a calculation produces a value that's either too big or too small for a given data type to hold. An example is trying to store the result of 300 x 300 in an 8-bit unsigned integer, which can only represent numbers from 0 to 255.
- Integer overflow. This specific case of arithmetic overflow occurs when an integer value goes beyond its maximum or below its minimum representable value. Depending on the system and context, this might wrap around (e.g., an 8-bit value exceeding 255 might wrap around to 0).
- Stack overflow. This is specific to the call stack in computer programs. Every time a function is called, a new stack frame is added to the call stack. If functions call themselves recursively without an exit condition (or with a very deep recursion), the stack can exceed its capacity, resulting in a stack overflow.
- Buffer overflow. This happens when a program writes more data to a buffer (like an array) than it can hold, causing data to spill over into adjacent memory areas. This can lead to unintended behavior, crashes, or security vulnerabilities.
- Floating point overflow. It occurs when a floating-point operation produces a result larger than the maximum value representable in its data type. There's also underflow in floating-point operations when the result is closer to zero than the smallest representable positive number in its data type.
Prevention of overflow errors
- Bounds checking. Before performing operations, especially arithmetic ones, check if the result will exceed the limits of the data type.
- Using larger data types. If you expect large values, use data types with a larger bit size (for example, a 64-bit integer instead of a 32-bit one).
- Error handling. Implement error handling in your program. If an overflow occurs, the program can detect it and respond appropriately, such as by giving an error message.
- Use safe math libraries. Some programming environments provide libraries that offer “safe” math operations. They check for overflows and other common pitfalls.
- Code reviews. Regularly review code, especially in critical systems, to check for potential overflow vulnerabilities..
