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Comment: fixed mapping notes space

Before the lifetime of the last pointer that stores the return value of a call to a standard memory allocation function has ended, it must be matched by a call to free() with that pointer value.

Noncompliant Code Example

In this noncompliant example, the object allocated by the call to malloc() is not freed before the end of the lifetime of the last pointer text_buffer referring to the object:

Code Block
bgColor#FFCCCC
langc
#include <stdlib.h>
 
enum { BUFFER_SIZE = 32 };

int f(void) {
  char *text_buffer = (char *)malloc(BUFFER_SIZE); 
  if (text_buffer == NULL) {
    return -1;
  }
  return 0;
}

Compliant Solution

In this compliant solution, the pointer is deallocated with a call to free():

Code Block
bgColor#ccccff
langc
#include <stdlib.h>

enum { BUFFER_SIZE = 32 };

int f(void) {
  char *text_buffer = (char *)malloc(BUFFER_SIZE); 
  if (text_buffer == NULL) {
    return -1;
  }
 
  free(text_buffer);
  return 0;
}

Exceptions

MEM31-C-EX1: Allocated memory does not need to be freed if it is assigned to a pointer with static storage duration whose lifetime is the entire execution of a program. The following code example illustrates a pointer that stores the return value from malloc() in a static variable:

Code Block
bgColor#ccccff
langc
#include <stdlib.h>
 
enum { BUFFER_SIZE = 32 };

int f(void) {
  static char *text_buffer = NULL;
  if (text_buffer == NULL) {
    text_buffer = (char *)malloc(BUFFER_SIZE); 
    if (text_buffer == NULL) {
      return -1;
    }
  }
  return 0;
}

Risk Assessment

Failing to free memory can result in the exhaustion of system memory resources, which can lead to a denial-of-service attack.

Rule

Severity

Likelihood

Remediation Cost

Priority

Level

MEM31-C

Medium

Probable

Medium

P8

L2

Automated Detection

Tool

Version

Checker

Description

Astrée
Include Page
Astrée_V
Astrée_V

Supported, but no explicit checker
Axivion Bauhaus Suite

Include Page
Axivion Bauhaus Suite_V
Axivion Bauhaus Suite_V

CertC-MEM31Can detect dynamically allocated resources that are not freed
CodeSonar
Include Page
CodeSonar_V
CodeSonar_V

ALLOC.LEAK

Leak

Compass/ROSE


Coverity

Include Page
Coverity_V
Coverity_V

RESOURCE_LEAK

ALLOC_FREE_MISMATCH

Finds resource leaks from variables that go out of scope while owning a resource

Cppcheck
 
Include Page
Cppcheck_V
Cppcheck_V
 leakReturnValNotUsedDoesn't use return value of memory allocation function
Klocwork
Include Page
Klocwork_V
Klocwork_V

MLK.MIGHT
MLK.MUST
MLK.RET.MUST
MLK.RET.MIGHT


LDRA tool suite
Include Page
LDRA_V
LDRA_V

50 D

Partially implemented
Parasoft C/C++test
Include Page
Parasoft_V
Parasoft_V

CERT_C-MEM31-a

Ensure resources are freed
Parasoft Insure++

Runtime analysis
Polyspace Bug Finder

Include Page
Polyspace Bug Finder_V
Polyspace Bug Finder_V

Memory leak

Memory allocated dynamically not freed

PRQA QA-C 9.11771
PRQA QA-C++4.2 3337, 3338 
SonarQube C/C++ Plugin
Include Page
SonarQube C/C++ Plugin_V
SonarQube C/C++ Plugin_V
S3584
Splint
Include Page
Splint_V
Splint_V


Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

Related Guidelines

Key here (explains table format and definitions)

Taxonomy

Taxonomy item

Relationship

ISO/IEC TR 24772:2013Memory Leak [XYL]Prior to 2018-01-12: CERT: Unspecified Relationship
ISO/IEC TS 17961Failing to close files or free dynamic memory when they are no longer needed [fileclose]Prior to 2018-01-12: CERT: Unspecified Relationship
CWE 2.11CWE-401, Improper Release of Memory Before Removing Last Reference ("Memory Leak")2017-07-05: CERT: Exact
CWE 2.11CWE-4042017-07-06: CERT: Rule subset of CWE
CWE 2.11CWE-4592017-07-06: CERT: Rule subset of CWE
CWE 2.11CWE-7712017-07-06: CERT: Rule subset of CWE
CWE 2.11CWE-7722017-07-06: CERT: Rule subset of CWE

CERT-CWE Mapping Notes

Key here for mapping notes

CWE-404/CWE-459/CWE-771/CWE-772 and FIO42-C/MEM31-C

Intersection( FIO42-C, MEM31-C) = Ø CWE-404 = CWE-459 = CWE-771 = CWE-772

CWE-404 = Union( FIO42-C, MEM31-C list) where list =

  • Failure to free resources besides files or memory chunks, such as mutexes)

Bibliography

[ISO/IEC 9899:2011]Subclause 7.22.3, "Memory Management Functions"