Page History

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#include <stdio.h>
#include <string.h>
 
int main(int argc, char *argv[]) {
  FILE *out;
  FILE *in;
  size_t size;
  char *ptr;
 
  if (argc != 2) {
    /* Handle error */
  }
 
  in = fmemopen(argv[1], strlen(argv[1]), "r");

  if (in == NULL){
    /* Handle error */
  }
  /* Use in */
 
  out = open_memstream(&ptr, &size);

  if (out == NULL){
    /* Handle error */
  }
  /* Use out */
  return 0;
}

Exceptions

POS54-C-EX1: The exception from EXP12-C. Do not ignore values returned by functions still applies. If the return value is inconsequential or if any errors can be safely ignored, such as for functions called because of their side effects, the function should be explicitly cast to void to signify programmer intentThis exception has been removed.

POS54-C-EX2: Ignore the return value of a function that cannot fail or whose return value cannot signify that an error condition need not be diagnosed. For example, strcpy() is one such function.

Return values from the following functions do not need to be checked because their historical use has overwhelmingly omitted error checking, and the consequences are not relevant to security.

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Function

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Successful Return

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Error Return

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printf()

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Number of characters (nonnegative)

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Negative

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putchar()

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Character written

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EOF

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puts()

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Nonnegative

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EOF (negative)

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putwchar()

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Wide character written

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WEOF

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vprintf()

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Number of characters (nonnegative)

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Negative

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vwprintf()

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Number of wide characters (nonnegative)

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Negative

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wprintf()

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Number of wide characters (nonnegative)

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The exception from ERR33-C. Detect and handle standard library errors (that is ERR33-C-EX1) applies to this rule. See that exception for more information.

Risk Assessment

Failing to detect error conditions can lead to unpredictable results, including abnormal program termination and denial-of-service attacks or, in some situations, could even allow an attacker to run arbitrary code.

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Related Vulnerabilities

The vulnerability in Adobe Flash [VU#159523] arises because Flash neglects to check the return value from calloc(). Even when calloc() returns NULL, Flash writes to an offset from the return value. Dereferencing NULL usually results in a program crash, but dereferencing an offset from NULL allows an exploit to succeed without crashing the program.

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