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Division and modulo operations are susceptible to divide-by-zero errors. 

C identifies two conditions The C Standard identifies the following condition under which division and modulo remainder operations result in undefined behavior (UB):

Ensure that division and remainder operations do not result in divide-by-zero errors.

Division

The result of the / operator is the quotient from the division of the first arithmetic operand by the second arithmetic operand. Division operations are susceptible to divide-by-zero errors. Overflow can also occur during two's complement signed integer division when the dividend is equal to the minimum (most negative) value for the signed integer type and the divisor is equal to −1. (See INT32-C. Ensure that operations on signed integers do not result in overflow.)

Noncompliant Code Example

This noncompliant code example can result in prevents signed integer overflow in compliance with INT32-C. Ensure that operations on signed integers do not result in overflow but fails to prevent a divide-by-zero error during the division of the signed operands sl1 and sl2.operands s_a and s_b:


#include <limits.h>
 
void func(signed long sl1s_a, sl2, signed long s_b) {
  signed long result;
  if ((s_a == LONG_MIN) && (s_b == -1)) {
    /* Initialize sl1 and sl2Handle error */
  } else {
    result = sl1s_a / sl2s_b;
  }
  /* ... */
}

Compliant Solution

This compliant solution tests the suspect division operation to guarantee there is no possibility of divide-by-zero errors or signed overflow.:

#include <limits.h>
 
void func(signed long sl1s_a, sl2, result;

/* Initialize sl1 and sl2 */

if ( (sl2signed long s_b) {
  signed long result;
  if ((s_b == 0) || ( (sl1s_a == LONG_MIN) && (sl2s_b == -1) ) ) {
    /* Handle error condition */
  }
 else {
    result = sl1s_a / sl2s_b;
  }
  /* ... */
}

...

Remainder

The modulo remainder operator provides the remainder when two operands of integer type are divided. 

Noncompliant Code Example

This noncompliant code example can result in example prevents signed integer overflow in compliance with INT32-C. Ensure that operations on signed integers do not result in overflow but fails to prevent a divide-by-zero error during the modulo remainder operation on the signed operands sl1 and sl2.operands s_a and s_b:

#include <limits.h>
 
void func(signed long sl1, sl2,s_a, signed long s_b) {
  signed long result;
  if ((s_a == LONG_MIN) && (s_b == -1)) {
    /* InitializeHandle sl1 anderror sl2 */
  } else {
    result = sl1s_a % sl2;
s_b;
  }
  /* ... */
}

Compliant Solution

This compliant solution tests the suspect modulo operation remainder operand to guarantee there is no possibility of a divide-by-zero error or an overflow error.:

#include <limits.h>
 
void func(signed long sl1s_a, sl2, result;

/* Initialize sl1 and sl2 */

if ( (sl2 signed long s_b) {
  signed long result;
  if ((s_b == 0 ) || ( (sl1s_a == LONG_MIN) && (sl2s_b == -1) ) ) {
    /* Handle error condition */
  }
 else {
    result = sl1s_a % sl2s_b;
  }
  /* ... */
}

Risk Assessment

A divide-by-zero error can result in abnormal program termination and denial of service.

Automated Detection

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

Related Guidelines

Key here (explains table format and definitions)

CERT-CWE Mapping Notes

Key here for mapping notes

CWE-682 and INT33-C

CWE-682 = Union( INT33-C, list) where list =

• Incorrect calculations that do not involve division by zero

Bibliography

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