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 (negative) value for the signed integer type and the divisor is equal to —1 (see NUM00-J. Detect or prevent integer overflow).

Noncompliant Code Example

This code can result in a divide-by-zero error during the division of the signed operands sl1 and sl2.

signed long sl1, sl2, result;

/* Initialize sl1 and sl2 */

result = sl1 / sl2;

Compliant Solution

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

signed long sl1, sl2, result;

/* Initialize sl1 and sl2 */

if ( (sl2 == 0) ) {
  /* handle error condition */
}
else {
  result = sl1 / sl2;
}

Modulo

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

Noncompliant Code Example

This code can result in a divide-by-zero error during the remainder operation on the signed operands sl1 and sl2.

signed long sl1, sl2, result;

/* Initialize sl1 and sl2 */

result = sl1 % sl2;

Compliant Solution

This compliant solution tests the suspect remainder operation to guarantee there is no possibility of a divide-by-zero error.

signed long sl1, sl2, result;

/* Initialize sl1 and sl2 */

if ( (sl2 == 0 ) ) {
  /* handle error condition */
}
else {
  result = sl1 % sl2;
}

Risk Assessment

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

Automated Detection

Automated detection exists for C and C++, but not for Java yet.

Related Vulnerabilities

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

Other Languages

This rule appears in the C Secure Coding Standard as INT33-C. Ensure that division and modulo operations do not result in divide-by-zero errors.
CERT C++ Secure Coding Standard: INT33-CPP. Ensure that division and modulo operations do not result in divide-by-zero errors

Bibliography

\[[ISO/IEC 9899:1999|AA. Bibliography#ISO/IEC 9899-1999]\] Section 6.5.5, "Multiplicative operators"
\[[MITRE 07|AA. Bibliography#MITRE 07]\] [CWE ID 369|http://cwe.mitre.org/data/definitions/369.html], "Divide By Zero"
\[[Seacord 05|AA. Bibliography#Seacord 05]\] Chapter 5, "Integers"
\[[Warren 02|AA. Bibliography#Warren 02]\] Chapter 2, "Basics"

INT32-CPP. Ensure that operations on signed integers do not result in overflow      04. Integers (INT)      INT34-CPP. Do not shift a negative number of bits or more bits than exist in the operand