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Risk Assessment Summary

Related Rules and Recommendations

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Memory management is a common source of programming flaws that can lead to security vulnerabilities. In the C programming language, decisions regarding how dynamic memory is allocated, used, and de-allocated are the burden of the programmer. Poor memory management can lead to security issues such as heap-buffer overflows, dangling pointers, and double-free issues Seacord 05 . From the programmer's perspective, memory management involves allocating memory, reading and writing to memory, and deallocating memory.

The following rules and recommendations are designed to reduce the common errors associated with memory management. These guidelines address common misunderstandings and errors in memory management that lead to security vulnerabilities.

These guidelines apply to the following standard memory management routines described in C99 Section 7.20.3:

void * malloc(size_t size);

void * calloc(size_t nmemb, size_t size);

void * realloc(void *ptr, size_t size);

void free(void *ptr);

The specific characteristics of these routines are based on the compiler used. With a few exceptions, this document only considers the general and compiler-independent attributes of these routines.

Recommendations

Allocate and free memory in the same module, at the same level of abstraction

Set pointers to dynamically allocated memory to NULL after they are released

Adopt consistent guidelines for memory allocation and de-allocation

Rules

Do not access freed memory

Do not free memory multiple times

Detect and handle memory allocation errors

Do not assume memory allocation routines initialize memory

Only free memory allocated dynamically

Ensure that size arguments to memory allocation functions are valid

Do not make assumptions about the result of allocating 0 bytes

Ensure that size arguments to calloc() do not result in an arithmetic overflow

References

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