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According to the C Standard, the library functions listed in the following table may contain data races when invoked by multiple threads.
| Functions | Remediation |
|---|---|
rand(), srand() | MSC30-C. Do not use the rand() function for generating pseudorandom numbers |
getenv(), getenv_s() | ENV34-C. Do not store pointers returned by certain functions |
strtok() | strtok_s() in C11 Annex Kstrtok_r() in POSIX |
strerror() | strerror_s() in C11 Annex Kstrerror_r() in POSIX |
asctime(), ctime(),localtime(), gmtime() | asctime_s(), ctime_s(), localtime_s(), gmtime_s() in C11 Annex K |
setlocale() | Protect multithreaded access to locale-specific functions with a mutex |
ATOMIC_VAR_INIT, atomic_init() | Do not attempt to initialize an atomic variable from multiple threads |
tmpnam() | tmpnam_s() in C11 Annex Ktmpnam_r() in POSIX |
mbrtoc16(), c16rtomb(),mbrtoc32(), c32rtomb() | Do not call with a null mbstate_t * argument |
Section 2.9.1 of the Portable Operating System Interface (POSIX®), Base Specifications, Issue 7 [IEEE Std 1003.1:2013] extends the list of functions that are not required to be thread-safe.
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In this noncompliant code example, the function f() is called from within a multithreaded application but encounters an error while calling a system function. The strerror() function returns a human-readable error string given an error number.
The C Standard, 7.2426.6.2 3 paragraph 3 [ISO/IEC 9899:20112024], specifically states that strerror() is not required to avoid data races.
The strerror function is not required to avoid data races with other calls to the strerror function.
An implementation could write the error string into a static array and return a pointer to it, and that array might be accessible and modifiable by other threads.
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This code first sets errno to 0 to comply with ERR30-C. Set errno to zero before calling a library function known to set errno, and check errno only after the function returns a value indicating failureTake care when reading errno.
Compliant Solution (Annex K, strerror_s())
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Race conditions caused by multiple threads invoking the same library function can lead to abnormal termination of the application, data integrity violations, or a denial-of-service attack.
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
CON33-C | Medium | Probable | High | P4 | L3 |
Related Vulnerabilities
Search for vulnerabilities resulting from the violation of this rule on the CERT website.
Automated Detection
Tool | Version | Checker | Description | ||||
|---|---|---|---|---|---|---|---|
| Astrée |
|
| Supported, but no explicit checker | |||||||||
| CodeSonar |
| BADFUNC.RANDOM.RAND | Use of | ||||||
| Compass/ROSE |
A module written in Compass/ROSE can detect violations of this rule | |||||||||
| Cppcheck Premium |
| premium-cert-con33-c | Fully implemented | ||||||
| Helix QAC |
| C5037 C++5021 DF4976, DF4977 | |||||||
| Klocwork |
| CERT.CONC.LIB_FUNC_USE | |||||||
| LDRA tool suite |
| 44 S | Partially Implemented | ||||||
| Parasoft C/C++test |
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CERT_C-CON33-a | Avoid using thread-unsafe functions | ||||||||
| PC-lint Plus |
| 586 | Fully supported | ||||||
| CERT C: Rule CON33-C | Checks for data race through standard library function call (rule fully covered) |
Related Guidelines
Key here (explains table format and definitions)
Taxonomy | Taxonomy item | Relationship |
|---|---|---|
| CERT C Secure Coding Standard | ERR30-C. Set errno to zero before calling a library function known to set errno, and check errno only after the function returns a value indicating failure | Prior to 2018-01-12: CERT: Unspecified Relationship |
| CERT C | CON00-CPP. Avoid assuming functions are thread safe unless otherwise specified | Prior to 2018-01-12: CERT: Unspecified Relationship |
| CWE 2.11 | CWE-330 | 2017-06-28: CERT: Partial overlap |
| CWE 2.11 | CWE-377 | 2017-06-28: CERT: Partial overlap |
| CWE 2.11 | CWE-676 | 2017-05-18: CERT: Rule subset of CWE |
CERT-CWE Mapping Notes
Key here for mapping notes
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- Invocation of other dangerous functions
Bibliography
| [IEEE Std 1003.1:2013] | Section 2.9.1, "Thread Safety" |
| [ISO/IEC 9899: |
| 2024] | Subclause 7. |
26.6. |
3, "The | |
| [Open Group 1997b] | Section 10.12, "Thread-Safe POSIX.1 and C-Language Functions" |
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