In software, a stack overflow occurs when too much memory
Computer memory
In computing, memory refers to the physical devices used to store programs or data on a temporary or permanent basis for use in a computer or other digital electronic device. The term primary memory is used for the information in physical systems which are fast In computing, memory refers to the...
In computer science, a call stack is a stack data structure that stores information about the active subroutines of a computer program. This kind of stack is also known as an execution stack, control stack, run-time stack, or machine stack, and is often shortened to just "the stack"...
. The call stack contains a limited amount of memory, often determined at the start of the program. The size of the call stack depends on many factors, including the programming language, machine architecture, multi-threading, and amount of available memory. When a program attempts to use more space than is available on the call stack (that is, when it attempts to access memory beyond the call stack's bounds, which is essentially a buffer overflow
Buffer overflow
In computer security and programming, a buffer overflow, or buffer overrun, is an anomaly where a program, while writing data to a buffer, overruns the buffer's boundary and overwrites adjacent memory. This is a special case of violation of memory safety....
), the stack is said to overflow, typically resulting in a program crash. This class of software bug is usually caused by one of two types of programming errors.
Infinite recursion
The most common cause of stack overflows is excessively deep or infinite recursion. Languages like Scheme, which implement tail-call optimization, allow infinite recursion of a specific sort—tail recursion—to occur without stack overflow. This works because tail-recursion calls do not take up additional stack space.
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
.
int foo {
return foo;
}
The function foo, when it is invoked, continues to invoke itself, using additional space on the stack each time, until the stack overflows resulting in a segmentation fault
Segmentation fault
A segmentation fault , bus error or access violation is generally an attempt to access memory that the CPU cannot physically address. It occurs when the hardware notifies an operating system about a memory access violation. The OS kernel then sends a signal to the process which caused the exception...
.
Very large stack variables
The other major cause of a stack overflow results from an attempt to allocate more memory on the stack than will fit. This is usually the result of creating local array variables that are far too large. For this reason arrays larger than a few kilobytes should be allocated dynamically instead of as a local variable.
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
:
int foo {
double x[1000000];
}
The declared array consumes 8 megabytes of data (assuming each double is 8 bytes); if this is more memory than is available on the stack, a stack overflow will occur.
Stack overflows are made worse by anything that reduces the effective stack size of a given program. For example, the same program being run without multiple threads might work fine, but as soon as multi-threading is enabled the program will crash. This is because most programs with threads have less stack space per thread than a program with no threading support. Similarly, people new to kernel development are usually discouraged from using recursive algorithms or large stack buffers.
In computer security and programming, a buffer overflow, or buffer overrun, is an anomaly where a program, while writing data to a buffer, overruns the buffer's boundary and overwrites adjacent memory. This is a special case of violation of memory safety....
In computer science, a call stack is a stack data structure that stores information about the active subroutines of a computer program. This kind of stack is also known as an execution stack, control stack, run-time stack, or machine stack, and is often shortened to just "the stack"...
A heap overflow is a type of buffer overflow that occurs in the heap data area. Heap overflows are exploitable in a different manner to that of stack-based overflows. Memory on the heap is dynamically allocated by the application at run-time and typically contains program data...
In software, a stack buffer overflow occurs when a program writes to a memory address on the program's call stack outside of the intended data structure; usually a fixed length buffer....
