CWE Rule 252

This issue occurs when you call sensitive standard functions that return information about possible errors and you do one of the following:

The checker considers a function as sensitive if the function call is prone to failure because of reasons such as:

The checker only considers functions where the return value indicates if the function completed without errors.

Some of these functions can perform critical tasks such as:

If you do not check the return value of functions that perform sensitive tasks and indicate error information through their return values, your program can behave unexpectedly. Errors from these functions can propagate throughout the program causing incorrect output, security vulnerabilities, and possibly system failures.

Before continuing with the program, test the return value of critical sensitive functions.

For sensitive functions that are not critical, you can explicitly ignore a return value by casting the function to void. Polyspace^® does not raise this defect for sensitive functions cast to void. This resolution is not accepted for critical sensitive functions because they perform more vulnerable tasks.

#include <pthread.h>
#include <string.h>
#include <stddef.h>
#include <stdio.h>

void initialize() {
    pthread_attr_t attr;

    pthread_attr_init(&attr);//Noncompliant 
}
int read_file(int argc, char *argv[])
{
  FILE *in;
  if (argc != 2) {
    /* Handle error */
  }

  in = fmemopen (argv[1], strlen (argv[1]), "r");   
  return 0; //Noncompliant

}

This example shows calls to the sensitive POSIX functions pthread_attr_init and fmemopen. Their return values are ignored, causing defect.

One possible correction is to cast the function to void. This fix informs Polyspace and any reviewers that you are explicitly ignoring the return value of the sensitive function.

#include <pthread.h>
#include <string.h>
#include <stddef.h>
#include <stdio.h>

void initialize() {
    pthread_attr_t attr;

    (void)pthread_attr_init(&attr);//Compliant 
}
int read_file(int argc, char *argv[])
{
  FILE *in;
  if (argc != 2) {
    /* Handle error */
  }

  (void)fmemopen (argv[1], strlen (argv[1]), "r"); //Compliant
  
  return 0; 
}

One possible correction is to test the return value of pthread_attr_init and fmemopen to check for errors.

#include <pthread.h>
#include <string.h>
#include <stddef.h>
#include <stdio.h>

void initialize() {
    pthread_attr_t attr;

    int result = pthread_attr_init(&attr);//Compliant 
	if(result != 0){
		//Handle fatal error
	} 
}
int read_file(int argc, char *argv[])
{
  FILE *in;
  if (argc != 2) {
    /* Handle error */
  }

  in = fmemopen (argv[1], strlen (argv[1]), "r"); 
  if (in==NULL){
	  // Handle error
  }
  return 0;//Compliant 
}

#include <pthread.h>
extern void *start_routine(void *);

void returnnotchecked() {
    pthread_t thread_id;
    pthread_attr_t attr;
    void *res;

    (void)pthread_attr_init(&attr);
    (void)pthread_create(&thread_id, &attr, &start_routine, ((void *)0));  //Noncompliant
    pthread_join(thread_id,  &res);  //Noncompliant
}

In this example, two critical functions are called: pthread_create and pthread_join. The return value of the pthread_create is ignored by casting to void, but because pthread_create is a critical function (not just a sensitive function), Polyspace does not ignore this Return value of a sensitive function not checked defect. The other critical function, pthread_join, returns value that is ignored implicitly. pthread_join uses the return value of pthread_create, which was not checked.

The correction for this defect is to check the return value of these critical functions to verify the function performed as expected.

#include <pthread.h>
#include <stdlib.h>
#define fatal_error() abort()

extern void *start_routine(void *);

void returnnotchecked() {
    pthread_t thread_id;
    pthread_attr_t attr;
    void *res;
    int result;

    (void)pthread_attr_init(&attr);
    result = pthread_create(&thread_id, &attr, &start_routine, NULL);
    if (result != 0) {
        /* Handle error */
        fatal_error();
    }

    result = pthread_join(thread_id,  &res);
    if (result != 0) {
        /* Handle error */
        fatal_error();
    }
}