SEI CERT C Coding Standard

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changes.mady.by.user Carol J. Lallier

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Dynamic memory management is a common source of programming flaws that can lead to security vulnerabilities. Decisions regarding how dynamic memory is allocated, used, and deallocated 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 2005a]. From the programmer's perspective, memory management involves allocating memory, reading and writing to memory, and deallocating memory.

Allocating and freeing memory in different modules and levels of abstraction may make it difficult to determine when and if a block of memory has been freed, leading to programming defects, such as memory leaks, double-free vulnerabilities, accessing freed memory, or writing to freed or unallocated memory.

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Failing to follow this recommendation has led to real-world vulnerabilities. For example, freeing memory in different modules resulted in a vulnerability in MIT Kerberos 5 [MIT 2004]. The MIT Kerberos 5 code in this case contained error-handling logic, which freed memory allocated by the ASN.1 decoders if pointers to the allocated memory were non-null. However, if a detectable error occurred, the ASN.1 decoders freed the memory that they had allocated. When some library functions received errors from the ASN.1 decoders, they also attempted to free the same memory, resulting in a double-free vulnerability.

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Tool

Version

Checker

Description

LDRA tool suite

Include Page
LDRA_V
LDRA_V

50 D

Partially implemented.

Fortify SCA

V. 5.0

 

Can detect violations of this rule with CERT C Rule Pack.

Compass/ROSE

 

 

Could detect possible violations by reporting any function that has malloc() or free() but not both. This would catch some false positives, as there would be no way to tell if malloc() and free() are at the same level of abstraction if they are in different functions.

Coverity Prevent

Include Page
Coverity_V
Coverity_V

USE_AFTER_FREE

Can detect the specific instances where memory is deallocated more than once or read/written to the target of a freed pointer.

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ISO/IEC 9899:2011 Section 7.23.3, "Memory management functions"

ISO/IEC TR 24772 "XYL Memory leak"

MITRE CWE: CWE-416, "Use after free"

MITRE CWE: CWE-415, "Double free"

Bibliography

[MIT 2004]
[Plakosh 2005]
[Seacord 2005a] Chapter 4, "Dynamic Memory Management"

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