50. POSIX (POS)

These are rules and recommendations for functions that are defined as part of the POSIX family of standards but are not included in ISO/IEC 9899-1999. These rules and recommendations are not part of the core standard because they do not apply in all C language applications and because they represent an incomplete list. The intent of providing these rules is to demonstrate how rules and recommendations for other standards or specific implementations may be integrated with the core C99 recommendations.

Recommendations

POS00-C. Avoid race conditions with multiple threads

POS01-C. Check for the existence of links when dealing with files

POS02-C. Follow the principle of least privilege

Rules

POS30-C. Use the readlink() function properly

POS31-C. Do not unlock or destroy another thread's mutex

POS32-C. When data must be accessed by multiple threads, provide a mutex and guarantee no adjacent data is also accessed.

POS33-C. Do not use vfork()

POS34-C. Do not call putenv() with a pointer to an automatic variable as the argument

POS35-C. Avoid race conditions while checking for the existence of a symbolic link

POS36-C. Observe correct revocation order while relinquishing privileges

POS37-C. Ensure that privilege relinquishment is successful

Risk Assessment

Recommendation	Severity	Likelihood	Remediation Cost	Priority	Level
POS00-C	medium	probable	high	P4	L3
POS01-C	medium	likely	high	P6	L2
POS02-C	high	likely	high	P9	L2

Rule	Severity	Likelihood	Remediation Cost	Priority	Level
POS30-C	high	probable	medium	P12	L1
POS31-C	medium	probable	high	P4	L3
POS32-C	medium	probable	medium	P8	L2
POS33-C	low	probable	low	P6	L2
POS34-C	high	unlikely	medium	P6	L2
POS35-C	high	likely	medium	P18	L1
POS36-C	high	probable	medium	P12	L1
POS37-C	high	probable	low	P18	L1