Signed integer overflow is undefined behavior (see undefined behavior 36 in Annex J of the C Standard). This means that implementations have a great deal of . Consequently, implementations have considerable latitude in how they deal with signed integer overflow.
An implementation may define the same modulo arithmetic for both unsigned as well as signed integers. On such an implementation, signed integers overflow by wrapping around to zero. An example of such an implementation is GNU GCC invoked with the -fwrapv
command-line option.
Other implementations may cause a hardware trap (also called an exceptional condition) to be generated when a signed integer overflows. On such implementations, a program that causes a signed integer to overflow will most likely abnormally exit. On a UNIX system, the result of such an event may be a signal sent to the process. An example of such an implementation is GNU GCC invoked with the -ftrapv
command-line option.
Other implementations still may simply assume that signed integers never overflow and generate object code accordingly. An example of such an implementation is GNU GCC invoked without either the -fwrapv
or the -ftrapv
option.
It is also possible for the same . (See MSC15-C. Do not depend on undefined behavior.) An implementation that defines signed integer types as being modulo, for example, need not detect integer overflow. Implementations may also trap on signed arithmetic overflows, or simply assume that overflows will never happen and generate object code accordingly. It is also possible for the same conforming implementation to emit code that exhibits different behavior in different contexts. For example, an implementation may determine that a signed integer loop control variable declared in a local scope cannot overflow and may emit efficient code based on the basis of that determination, while the same implementation may avoid making that assumption in another function when the variable is a global objectdetermine that a global variable used in a similar context will wrap.
For these reasons, it is important to ensure that operations on signed integers do no not result in overflow. (See MSC15-C. Do not depend on undefined behavior. ) Of particular importance are operations on signed integer values that originate from untrusted sources a tainted source and are used in any of the following ways:as
- Integer operands of
- As an array index
- In any pointer arithmetic
- As a length or size of an object
- As the bound of an array (for example, a loop counter)
- , including array indexing
- The assignment expression for the declaration of a variable length array
- The postfix expression preceding square brackets
[]
or the expression in square brackets[]
of a subscripted designation of an element of an array object - Function arguments of type
size_t
orrsize_t
(for example, As an argument to a memory allocation function - In security-critical code
- )
Integer operations will Most integer operations can result in overflow if the resulting value cannot be represented by the underlying representation of the integer. The following table indicates which operators operations can result in overflow:.
Operator | Overflow |
---|
Operator | Overflow |
---|
Operator | Overflow |
---|
Operator | Overflow |
---|---|
| Yes |
| Yes |
| Yes |
| No | |
| Yes |
| Yes |
| No |
| No | |
| Yes |
| Yes |
| No |
| No |
| Yes |
| Yes |
| No |
| No |
| Yes |
| Yes |
| No |
| No | |
| Yes |
| No |
| No |
| No |
| Yes |
| No |
| No |
| No |
| No |
| No |
| No |
| No | |
| Yes |
| No |
| Yes |
| No |
The following sections examine specific operations that are susceptible to integer overflow. When operating on small integer types (smaller with less precision than int
), integer promotions are applied. The usual arithmetic conversions may also be applied to (implicitly) convert operands to equivalent types before arithmetic operations are performed. Make sure you Programmers should understand integer conversion rules before trying to implement secure arithmetic operations. (See INT02-C. Understand integer conversion rules.) Anchor
Addition
Addition is between two operands of arithmetic type or between a pointer to an object type and an integer type for rules about adding a pointer to an integer. (See ARR37-C. Do not add or subtract an integer to a pointer to a non-array object and ARR38-C. Do not add or subtract an integer to a pointer if the resulting value does not refer to a valid array element.) Incrementing is equivalent to adding 1.
Noncompliant Code Example
This noncompliant code example may result in a signed integer overflow during the addition of the signed operands si_a
and si_b
. If this behavior is unanticipated, it can lead to an exploitable vulnerability.
Code Block | ||||
---|---|---|---|---|
| ||||
int si_a;
int si_b;
int sum;
/* Initialize si_a and si_b */
sum = si_a + si_b;
|
Compliant Solution (Precondition Test, Two's Complement)
This compliant solution performs a precondition test of the operands of the addition to ensure no overflow occurs, assuming two's complement representation:
Code Block | ||||
---|---|---|---|---|
| ||||
signed int si_a;
signed int si_b;
signed int sum;
/* Initialize si_a and si_b */
if ( ((si_a^si_b) | (((si_a^(~(si_a^si_b) & INT_MIN)) + si_b)^si_b)) >= 0) {
/* Handle error condition */
} else {
sum = si_a + si_b;
}
|
This compliant solution works only on architectures that use two's complement representation. Although most modern platforms use two's complement representation, it is best not to introduce unnecessary platform dependencies. (See MSC14-C. Do not introduce unnecessary platform dependencies.) This solution can also be more expensive than a postcondition test, especially on RISC CPUs.
Compliant Solution (General)
This compliant solution tests the suspect addition operation to ensure no overflow occurs regardless of representation:
Code Block | ||||
---|---|---|---|---|
| ||||
signed int si_a;
signed int si_b;
signed int sum;
/* Initialize si_a and si_b */
if (((si_b>0) && (si_a > (INT_MAX-si_b)))
|| ((si_b<0) && (si_a < (INT_MIN-si_b)))) {
/* Handle error condition */
}
else {
sum = si_a + si_b;
}
|
This solution is more readable but may be less efficient than the solution that is specific to two's complement representation.
...
Implementation Details
GNU GCC invoked with the -fwrapv
command-line option defines the same modulo arithmetic for both unsigned and signed integers.
GNU GCC invoked with the -ftrapv
command-line option causes a trap to be generated when a signed integer overflows, which will most likely abnormally exit. On a UNIX system, the result of such an event may be a signal sent to the process.
GNU GCC invoked without either the -fwrapv
or the -ftrapv
option may simply assume that signed integers never overflow and may generate object code accordingly.
Atomic Integers
The C Standard defines the behavior of arithmetic on atomic signed integer types to use two's complement representation with silent wraparound on overflow; there are no undefined results. Although defined, these results may be unexpected and therefore carry similar risks to unsigned integer wrapping. (See INT30-C. Ensure that unsigned integer operations do not wrap.) Consequently, signed integer overflow of atomic integer types should also be prevented or detected.
Addition
Addition is between two operands of arithmetic type or between a pointer to an object type and an integer type. This rule applies only to addition between two operands of arithmetic type. (See ARR37-C. Do not add or subtract an integer to a pointer to a non-array object and ARR30-C. Do not form or use out-of-bounds pointers or array subscripts.)
Incrementing is equivalent to adding 1.
Noncompliant Code Example
This noncompliant code example can result in a signed integer overflow during the addition of the signed operands si_a
and si_b
:
Code Block | ||||
---|---|---|---|---|
| ||||
void func(signed int si_a, signed int si_b) {
signed int sum = si_a + si_b;
/* ... */
} |
Compliant Solution
This compliant solution ensures that the addition operation cannot overflow, regardless of representation:
Code Block | ||||
---|---|---|---|---|
| ||||
#include <limits.h>
void f(signed int si_a, signed int si_b) {
signed int sum;
if (((si_b > 0) && (si_a > (INT_MAX - si_b))) ||
((si_b < 0) && (si_a < (INT_MIN - si_b)))) {
/* Handle error */
} else {
sum = si_a + si_b;
}
/* ... */
} |
Compliant Solution (GNU)
This compliant solution uses the GNU extension __builtin_sadd_overflow
, available with GCC, Clang, and ICC:
Code Block | ||||
---|---|---|---|---|
| ||||
void f(signed int si_a, signed int si_b) {
signed int sum;
if (__builtin_sadd_overflow(si_a, si_b, &sum)) {
/* Handle error */
}
/* ... */
} |
Subtraction
...
Subtraction
Subtraction is between two operands of arithmetic type, two pointers to qualified or unqualified versions of compatible object types, or a pointer to an object type and an integer type. This rule applies only to subtraction between two operands of arithmetic type. (See ARR36-C. Do not subtract or compare two pointers that do not refer to the same array, ARR37-C. Do not add or subtract an integer to a pointer to a non-array object, and ARR38and ARR30-C. Do not add or subtract an integer to a pointer if the resulting value does not refer to a valid array elementform or use out-of-bounds pointers or array subscripts for information about pointer subtraction.)
Decrementing is equivalent to subtracting one1.
Noncompliant Code Example
This noncompliant code example can result in a signed integer overflow during the subtraction of the signed operands si_a
and si_b
. If this behavior is unanticipated, the resulting value may be used to allocate insufficient memory for a subsequent operation or in some other manner that can lead to an exploitable vulnerability.:
Code Block | ||||
---|---|---|---|---|
| ||||
void func(signed int si_a; , signed int si_b;) { signed int result; /* Initializediff = si_a and- si_b */; result = si_a - si_b; /* ... */ } |
Compliant Solution
...
This compliant solution tests the operands of the subtraction to guarantee there is no possibility of signed overflow, presuming two's complement regardless of representation:
Code Block | ||||
---|---|---|---|---|
| ||||
#include <limits.h> void func(signed int si_a; , signed int si_b;) { signed int resultdiff; /* Initializeif ((si_b > 0 && si_a and < INT_MIN + si_b) */ if|| (((si_a^si_b) < 0 && (((si_a ^ ((si_a^si > INT_MAX + si_b)) { &/* (1Handle <<error (sizeof(int)*CHAR_BIT-1))))-si_b)^si_b)) < 0) { /* Handle error condition */ } else { result */ } else { diff = si_a - si_b; } /* ... */ } |
This compliant solution only works on architectures that use two's complement representation. Although most modern platforms use two's complement representation, it is best not to introduce unnecessary platform dependencies. (See MSC14-C. Do not introduce unnecessary platform dependencies.)
Compliant Solution (General)
Compliant Solution (GNU)
This compliant solution uses the GNU extension __builtin_ssub_overflow
, available with GCC, Clang, and ICCThis compliant solution tests the operands of the subtraction to guarantee there is no possibility of signed overflow, regardless of representation:
Code Block | ||||
---|---|---|---|---|
| ||||
void func(signed int si_a; , signed int si_b; singed) { signed int resultdiff; /* Initialize si_a and si_b */ if ((si_b > 0 && __builtin_ssub_overflow(si_a < INT_MIN + , si_b, &diff)) ||{ (si_b < 0 && si_a > INT_MAX + si_b)) {/* Handle error */ } /* Handle error condition */ } else { result = si_a - si_b; } |
...
... */
} |
Multiplication
Multiplication is between two operands of arithmetic type.
Noncompliant Code Example
This noncompliant code example can result in a signed integer overflow during the multiplication of the signed operands si_a
and si_b
. If this behavior is unanticipated, the resulting value may be used to allocate insufficient memory for a subsequent operation or in some other manner that can lead to an exploitable vulnerability.:
Code Block | ||||
---|---|---|---|---|
| ||||
Code Block | ||||
| ||||
void func(signed int si_a; , signed int si_b;) { signed int result; /* ... */ result = si_a * si_b; /* ... */ } |
Compliant Solution
This compliant solution guarantees there is no possibility of The product of two operands can always be represented using twice the number of bits than exist in the precision of the larger of the two operands. This compliant solution eliminates signed overflow on systems where long long
is at least twice the size precision of int
:
Code Block | ||||
---|---|---|---|---|
| ||||
signed int si_a; signed int si_b; signed int result; /* Initialize si_a and si_b */ static_assert( sizeof(long long#include <stddef.h> #include <assert.h> #include <limits.h> #include <inttypes.h> extern size_t popcount(uintmax_t); #define PRECISION(umax_value) popcount(umax_value) void func(signed int si_a, signed int si_b) { signed int result; signed long long tmp; assert(PRECISION(ULLONG_MAX) >= 2 * sizeofPRECISION(int), "Unable to detect overflow after multiplication" UINT_MAX)); signed long long tmp = (signed long long)si_a * (signed long long)si_b; /* * If the product cannot be represented as a 32-bit integer, * handle as an error condition. */ if ( (tmp > INT_MAX) || (tmp < INT_MIN) ) { /* Handle error condition */ } else { result = (int)tmp; } |
The compliant solution uses a static assertion to ensure that the overflow detection will succeed. See DCL03-C. Use a static assertion to test the value of a constant expression for a discussion of static assertions.
/* ... */
} |
The assertion fails if long long
has less than twice the precision of int
. The PRECISION()
macro and popcount()
function provide the correct precision for any integer type. (See INT35-C. Use correct integer precisions.)
Compliant Solution
The following portable compliant solution can be used with any conforming implementation, including those that do not have an integer type that is at least twice the precision of int
On systems where this relationship does not exist, the following compliant solution may be used to ensure signed overflow does not occur:
Code Block | ||||
---|---|---|---|---|
| ||||
#include <limits.h> void func(signed int si_a; , signed int si_b;) { signed int result; /* Initializeif (si_a and si_b */ if (si_a > > 0) { /* si_a is positive */ if (si_b > 0) { /* si_a and si_b are positive */ if (si_a > (INT_MAX / si_b)) { /* Handle error condition */ } } /* end if si_a and si_b are positive */ } else { /* si_a positive, si_b non-positivenonpositive */ if (si_b < (INT_MIN / si_a)) { /* Handle error condition */ } } /* si_a positive, si_b non-positivenonpositive */ } else { /* end if si_si_a is positivenonpositive */ else { /* si_a is non-positive */ if (si_b > 0) { /* si_a is non-positivenonpositive, si_b is positive */ if (si_a < (INT_MIN / si_b)) { /* Handle error condition */ } } /* end if si_a is non-positive, si_b is positive */ } else { /* si_a and si_b are non-positivenonpositive */ if ( (si_a != 0) && (si_b < (INT_MAX / si_a))) { /* Handle error condition */ } } /* endEnd if si_a and si_b are non-positivenonpositive */ } /* endEnd if si_a is non-positivenonpositive */ result = si_a * si_b; |
...
} |
Compliant Solution (GNU)
This compliant solution uses the GNU extension __builtin_smul_overflow
, available with GCC, Clang, and ICC:
Code Block | ||||
---|---|---|---|---|
| ||||
void func(signed int si_a, signed int si_b) {
signed int result;
if (__builtin_smul_overflow(si_a, si_b, &result)) {
/* Handle error */
}
} |
Division
Division is between two operands of arithmetic type. Overflow can 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
. Division operations are also susceptible to divide-by-zero errors. (See INT33-C. Ensure that division and remainder operations do not result in divide-by-zero errors.)
Noncompliant Code Example
This noncompliant code example prevents divide-by-zero errors in compliance with INT33-C. Ensure that division and remainder operations do not result in divide-by-zero errors but does not prevent a signed integer overflow error in two's-complement.
Code Block | ||||
---|---|---|---|---|
| ||||
void func(signed long s_a, signed long s_b) {
signed long result;
if |
...
Division
Division is between two operands of arithmetic type. Overflow can 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. Division operations are also susceptible to divide-by-zero errors. (See INT33-C. Ensure that division and modulo operations do not result in divide-by-zero errors.)
Noncompliant Code Example
This noncompliant code example can result in a signed integer overflow during the division of the signed operands s_a
and s_b
or in a divide-by-zero error. The IA-32 architecture, for example, requires that both conditions result in a fault, which can easily result in a denial-of-service attack.
Code Block | ||||
---|---|---|---|---|
| ||||
signed long s_a;
signed long s_b;
signed long result;
/* Initialize s_a and s_b */
result = s_a / s_b;
|
Compliant Solution
This compliant solution guarantees there is no possibility of signed overflow or divide-by-zero errors:
Code Block | ||||
---|---|---|---|---|
| ||||
signed long s_a; signed long s_b; signed long result; /* Initialize s_a and s_b */ if ( (s_b == 0) ||{ ( (s_a == LONG_MIN) && (s_b == -1) ) ) { /* Handle error condition */ } /* Handle error */ } else { result = s_a / s_b; } /* ... */ } |
...
Implementation Details
On the x86-32 architecture, overflow results in a fault, which can be exploited as a denial-of-service attack.
Compliant Solution
This compliant solution eliminates the possibility of divide-by-zero errors or signed overflow:
Code Block | ||||
---|---|---|---|---|
| ||||
#include <limits.h>
void func(signed long s_a, |
...
Modulo
The modulo operator provides the remainder when two operands of integer type are divided.
Noncompliant Code Example
This noncompliant code example can result in a divide-by-zero error. Furthermore, many hardware platforms implement modulo as part of the division operator, which can overflow. Overflow can occur during a modulo operation when the dividend is equal to the minimum (negative) value for the signed integer type and the divisor is equal to −1. This occurs despite that the result of such a modulo operation should theoretically be 0.
Code Block | ||||
---|---|---|---|---|
| ||||
signed long s_a; signed long s_b; b) { signed long result; result = if ((s_b == 0) || ((s_a % s_b; |
Implementation Details
On x86 platforms, the modulo operator for signed integers is implemented by the idiv
instruction code, along with the divide operator. Because INT_MIN / -1
overflows, this code will throw a floating-point exception on INT_MIN % -1
.
On MSVC++, taking the modulo of INT_MIN
by −1 yields the value 0. On GCC/Linux, taking the modulo of INT_MIN
by −1 produces a floating-point exception. However, on GCC versions 4.2.4 and newer, with optimization enabled, taking the modulo of INT_MIN
by −1 yields the value 0.
Compliant Solution (Overflow Prevention)
This compliant solution tests the modulo operand to guarantee there is no possibility of a divide-by-zero error or an (internal) overflow error:
== LONG_MIN) && (s_b == -1))) {
/* Handle error */
} else {
result = s_a / s_b;
}
/* ... */
} |
Remainder
The remainder operator provides the remainder when two operands of integer type are divided. Because many platforms implement remainder and division in the same instruction, the remainder operator is also susceptible to arithmetic overflow and division by zero. (See INT33-C. Ensure that division and remainder operations do not result in divide-by-zero errors.)
Noncompliant Code Example
Many hardware architectures implement remainder as part of the division operator, which can overflow. Overflow can occur during a remainder operation when the dividend is equal to the minimum (negative) value for the signed integer type and the divisor is equal to −1. It occurs even though the result of such a remainder operation is mathematically 0. This noncompliant code example prevents divide-by-zero errors in compliance with INT33-C. Ensure that division and remainder operations do not result in divide-by-zero errors but does not prevent integer overflow:
Code Block | ||||
---|---|---|---|---|
| ||||
void func(signed long s_a, signed long s_b) {
signed long result;
if | ||||
Code Block | ||||
| ||||
signed long s_a; signed long s_b; signed long result; /* Initialize s_a and s_b */ if ( (s_b == 0 ) || ( (s_a == LONG_MIN) && (s_b == -10) ){ ) { /* Handle error condition */ } else { result result = s_a % s_b; } /* ... */ |
Compliant Solution (Absolute Value)
This compliant solution is based on the fact that both the division and modulo operators truncate toward 0, as specified in section 6.5.5, footnote 105, of the C Standard [ISO/IEC 9899:2011]. This guarantees that
Code Block |
---|
i % j
|
and
Code Block |
---|
i % -j
|
are always equivalent.
} |
Implementation Details
On x86-32 platforms, the remainder operator for signed integers is implemented by the idiv
instruction code, along with the divide operator. Because LONG_MIN / −1
overflows, it results in a software exception with LONG_MIN % −1
as well.
Compliant Solution
This compliant solution also tests the remainder operands to guarantee there is no possibility of an overflowFurthermore, it guarantees that the minimum signed value modulo −1 yields 0:
Code Block | ||||
---|---|---|---|---|
| ||||
#include <limits.h> void func(signed long s_a; , signed long s_b;) { signed long result; /* Initialize if ((s_b == 0 ) || ((s_a and== sLONG_b */ ifMIN) && (s_b == 0-1))) { /* Handle error condition */ } else { if (( result = s_ba < 0) && (% s_b; != LONG_MIN)) { s_b = -s_b; } } result = s_a % s_b; } |
...
Unary Negation
The unary negation operator takes an operand of arithmetic type. Overflow can occur during two's complement unary negation when the operand is equal to the minimum (negative) value for the signed integer type.
Noncompliant Code Example
This noncompliant code example can result in a signed integer overflow during the unary negation of the signed operand s_a
:
Code Block | ||||
---|---|---|---|---|
| ||||
signed long s_a;
signed long result;
/* Initialize s_a */
result = -s_a;
|
Compliant Solution
This compliant solution tests the suspect negation operation to guarantee there is no possibility of signed overflow:
Code Block | ||||
---|---|---|---|---|
| ||||
signed long s_a;
signed long result;
/* Initialize s_a */
if (s_a == INT_MIN) {
/* Handle error condition */
}
else
result = -s_a;
}
|
...
/* ... */
} |
Left-Shift Operator
The left-shift operator takes two integer operands. The result of E1 << E2
is E1
left-shifted E2
bit positions; vacated bits are filled with zeros.
The C Standard, 6.5.8, paragraph 4 [ISO/IEC 9899:2024], states
If
E1
has a signed type and nonnegative value, andE1 × 2E2
is representable in the result type, then that is the resulting value; otherwise, the behavior is undefined.
In almost every case, an attempt to shift by a negative number of bits or by more bits than exist in the operand indicates a logic error. These issues are covered by INT34-C. Do not shift an expression by a negative number of bits or by greater than or equal to the number of bits that exist in the operand.
Noncompliant Code Example
This noncompliant code example performs a left shift, after verifying that the number being shifted is not negative, and the number of bits to shift is valid. The PRECISION()
macro and popcount()
function provide the correct precision for any integer type. (See INT35-C. Use correct integer precisions.) However, because this code does no overflow check, it can result in an unrepresentable value.
Code Block | ||||
---|---|---|---|---|
| ||||
#include <limits.h>
#include <stddef.h>
#include <inttypes.h>
extern size_t popcount(uintmax_t);
#define PRECISION(umax_value) popcount(umax_value)
void func(signed long si_a, signed long si_b) {
signed long result;
if ((si_a < 0) || (si_b < 0) ||
(si_b >= PRECISION(ULONG_MAX))) {
/* Handle error */
} else {
result |
...
Left-Shift Operator
The left-shift operator is between two operands of integer type.
Noncompliant Code Example
This noncompliant code example can result in signed integer overflow:
Code Block | ||||
---|---|---|---|---|
| ||||
int si_a; int si_b; int sresult; /* Initialize si_a and si_b */ sresult = si_a << si_b; } /* ... */ } |
Compliant Solution
This compliant solution eliminates the possibility of overflow resulting from a left-shift operation:
Code Block | ||||
---|---|---|---|---|
| ||||
int si_a; int si_b; int sresult; /* Initialize si_a and si_b */ if ( #include <limits.h> #include <stddef.h> #include <inttypes.h> extern size_t popcount(uintmax_t); #define PRECISION(umax_value) popcount(umax_value) void func(signed long si_a, signed long si_b) { signed long result; if ((si_a < 0) || (si_b < 0) || (si_b >= sizeofPRECISION(int)*CHAR_BITULONG_MAX)) || (si_a > (INTLONG_MAX >> si_b)) ) { /* Handle error condition */ } else { sresult result = si_a << si_b; } |
This solution is also compliant with INT34-C. Do not shift a negative number of bits or more bits than exist in the operand.
Atomic Integers
The C Standard defines the behavior of arithmetic on atomic signed integer types to use two's complement representation with silent wraparound on overflow; there are no undefined results. However, although defined, these results may be unexpected and therefore carry similar risks to unsigned integer wrapping (see INT30-C. Ensure that unsigned integer operations do not wrap). Consequently, signed integer overflow of atomic integer types should also be prevented or detected.
This section includes an example for the addition of atomic integer types only. For other operations, you can use tests similar to the precondition tests for two’s complement integers used for nonatomic integer types.
Noncompliant Code Example
/* ... */
} |
Unary Negation
The unary negation operator takes an operand of arithmetic type. Overflow can occur during two's complement unary negation when the operand is equal to the minimum (negative) value for the signed integer type.
Noncompliant Code Example
This noncompliant code example can result in a signed integer overflow during the unary negation of the signed operand s_a
This noncompliant code example using atomic integers can result in unexpected signed integer overflow:
Code Block | ||||
---|---|---|---|---|
| ||||
atomic_int i; int si_a; /* Initialize i, si_a */ atomic_fetch_add(&i, si_a); void func(signed long s_a) { signed long result = -s_a; /* ... */ } |
Compliant Solution
This compliant solution tests the operands negation operation to guarantee there is no possibility of signed overflow. It loads the value stored in the atomic integer and tests for possible overflow before performing the addition:
Code Block | ||||
---|---|---|---|---|
| ||||
atomic_int i; int si_a; /* Initialize si_a, i */ int si_b = atomic_load(&i); if (((si_b>0) && (si_a > (INT_MAX-si_b))) || ((si_b<0) && (si_a < (INT_MIN-si_b)))) { #include <limits.h> void func(signed long s_a) { signed long result; if (s_a == LONG_MIN) { /* Handle error condition */ } else { atomic_fetch_add(&i, si_a); } result = -s_a; } /* ... */ } |
Risk Assessment
Integer overflow can lead to buffer overflows and the execution of arbitrary code by an attacker.
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
---|---|---|---|---|---|
INT32-C | high | likely | high | P9 | L2 |
Automated Detection
...
Tool
...
Version
...
Checker
...
Description
...
Fortify SCA
...
5.0
...
Can detect violations of this rule with CERT C Rule Pack. Specifically, it checks to ensure that the operand of a unary negation
is compared to the type's minimum value immediately before the operation
attacker.
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
---|---|---|---|---|---|
INT32-C | High | Likely | High | P9 | L2 |
Automated Detection
Tool | Version | Checker | Description | ||||||
---|---|---|---|---|---|---|---|---|---|
Astrée |
| integer-overflow | Fully checked | ||||||
CodeSonar |
| ALLOC.SIZE.ADDOFLOW | Addition overflow of allocation size | ||||||
Coverity |
| TAINTED_SCALAR BAD_SHIFT | Implemented | ||||||
Cppcheck Premium |
| premium-cert-int32-c | Partially implemented | ||||||
Helix QAC |
| C2800, C2860 C++2800, C++2860 DF2801, DF2802, DF2803, DF2861, DF2862, DF2863 | |||||||
Klocwork |
| NUM.OVERFLOW | |||||||
LDRA tool suite |
| 493 S, 494 S | Partially implemented | ||||||
Parasoft C/C++test |
| CERT_C-INT32-a | Avoid signed integer overflows | ||||||
Parasoft Insure++ | Runtime analysis | ||||||||
Polyspace Bug Finder |
| Checks for:
Rule partially covered. | |||||||
PVS-Studio |
| V1026, V1070, V1081, V1083, V1085, V5010 | |||||||
TrustInSoft Analyzer |
| signed_overflow | Exhaustively verified (see one compliant and one non-compliant example). |
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-20 and INT32-C
See CWE-20 and ERR34-C
CWE-680 and INT32-C
Intersection( INT32-C, MEM35-C) = Ø
Intersection( CWE-680, INT32-C) =
- Signed integer overflows that lead to buffer overflows
CWE-680 - INT32-C =
- Unsigned integer overflows that lead to buffer overflows
INT32-C – CWE-680 =
- Signed integer overflows that do not lead to buffer overflows
CWE-191 and INT32-C
Union( CWE-190, CWE-191) = Union( INT30-C, INT32-C)
Intersection( INT30-C, INT32-C) == Ø
Intersection(CWE-191, INT32-C) =
- Underflow of signed integer operation
CWE-191 – INT32-C =
- Underflow of unsigned integer operation
INT32-C – CWE-191 =
- Overflow of signed integer operation
CWE-190 and INT32-C
Union( CWE-190, CWE-191) = Union( INT30-C, INT32-C)
Intersection( INT30-C, INT32-C) == Ø
Intersection(CWE-190, INT32-C) =
- Overflow (wraparound) of signed integer operation
CWE-190 – INT32-C =
- Overflow of unsigned integer operation
INT32-C – CWE-190 =
- Underflow of signed integer operation
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43 D
493 S
494 S
...
0278
0296
0297
2800
...
Related Vulnerabilities
Search for vulnerabilities resulting from the violation of this rule on the CERT website.
Related Guidelines
...
Bibliography
[Dowd 2006] | Chapter 6, "C Language Issues" ("Arithmetic Boundary Conditions," pp. 211–223) |
[ |
ISO/IEC 9899:2024] | Subclause 6.5.8, "Bitwise shift operators" |
[Seacord 2013b] | Chapter 5, "Integer Security" |
[Viega 2005] | Section 5.2.7, "Integer Overflow" |
[ |
Warren 2002] | Chapter 2, "Basics" |
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