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

Ensure that division and remainder operations do not result in Division and modulo operations are susceptible to 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 −1. (see See INT32-C. Ensure that operations on signed integers do not result in overflow.).

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Noncompliant Code Example

This code can result in noncompliant code 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 division of the signed operands sl1 and sl2.operands s_a and s_b:


#include <limits.h>
 
void func(signed long sl1, sl2, result;

result = sl1 / sl2;
s_a, signed long s_b) {
  signed long result;
  if ((s_a == LONG_MIN) && (s_b == -1)) {
    /* Handle error */
  } else {
    result = s_a / s_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, signed long s_b) {
  signed long result;

  if ( (sl2s_b == 0) || ( (sl1s_a == LONG_MIN) && (sl2s_b == -1) ) ) {
    /* handleHandle error condition */
  } else {
    result = sl1s_a / sl2;

Modulo

s_b;
  }
  /* ... */
}

Remainder

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

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Noncompliant Code Example

This code can result in noncompliant code 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, result;

result = sl1 % sl2;
s_a, signed long s_b) {
  signed long result;
  if ((s_a == LONG_MIN) && (s_b == -1)) {
    /* Handle error */
  } else {
    result = s_a % 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 sl1, sl2,s_a, signed long s_b) {
  signed long result;

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

Risk Assessment

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

Automated Detection

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Related Vulnerabilities

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

References

\[[ISO/IEC 9899-1999|AA. C References#ISO/IEC 9899-1999]\] Section 6.5.5, "Multiplicative operators"
\[[Seacord 05|AA. C References#Seacord 05]\] Chapter 5, "Integers"
\[[Warren 02|AA. C References#Warren 02]\] Chapter 2, "Basics"

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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Image Added Image Added Image AddedImage Removed      04. Integers (INT)       INT34-C. Arguments to character handling functions must be representable as an unsigned char