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CodeSonar® 9.2p0 CONFIDENTIAL CodeSecure Inc
C and C++

MISC.MEM.SIZE.TRUNC : Truncation of Size

Summary

A size argument to one of the triggering functions is based on a calculation that may involve truncation, thus risking an unexpectedly small operation scope.

(Note: When truncation can affect size calculation for a memory allocation, warning class Truncation of Allocation Size applies instead.)

Properties

Class Name Truncation of Size
Significance security
Mnemonic MISC.MEM.SIZE.TRUNC
Categories
MisraC2025 MisraC2025:21.18 The size_t argument passed to any function in <string.h> shall have an appropriate value
MisraC2023 MisraC2023:21.18 The size_t argument passed to any function in <string.h> shall have an appropriate value
Misra2012 Misra2012:21.18 The size_t argument passed to any function in <string.h> shall have an appropriate value
AUTOSARC++14 AUTOSARC++14:A4-7-1 An integer expression shall not lead to data loss.
MisraC++2023 MisraC++2023:0.3.2 A function call shall not violate the function's preconditions
CWE CWE:192 Integer Coercion Error
  CWE:197 Numeric Truncation Error
  CWE:680 Integer Overflow to Buffer Overflow
TS17961 TS17961:5.45-taintsink Tainted, potentially mutilated, or out-of-domain integer values are used in a restricted sink
CERT-C CERT-C:INT02-C Understand integer conversion rules
  CERT-C:INT18-C Evaluate integer expressions in a larger size before comparing or assigning to that size
  CERT-C:INT31-C Ensure that integer conversions do not result in lost or misinterpreted data
JSF++ JSF++:203 Evaluation of expressions shall not lead to overflow/underflow (unless required algorithmically and then should be heavily documented).
  JSF++:212 Underflow or overflow functioning shall not be depended on in any special way.
Availability Available for C and C++.
Enabling Checks for this warning class are disabled by default. To enable them, add the following WARNING_FILTER rule to the project configuration file. 
WARNING_FILTER += allow class="Truncation of Size"

Example 

#include <string.h>

void do_trunc_size(char *p, int x)
{
    memset(p, 0, (short) x);  /* Truncation of Size
                               * warning issued here. */
    /* ... */
}

Triggers

CodeSonar ships with library models that allow it to recognize a large number of functions that operate on memory and take a size argument. Some examples are shown in the table below. If one of these functions is called with a size argument that may have undergone truncation, a warning will be issued.

If you have created a custom library model for some function f() in terms of one of these existing models, calls to f() will also be capable of triggering Truncation of Size warnings.

Functions that can trigger warnings include...
Apache Portable Runtime (APR) apr_cpystrn(), apr_pmemdup()
gcc Builtins __builtin___memcpy_chk(), __builtin_strncpy()
LDAP ldap_search_ext()
libc memcpy(), strncat(), write()
libpq PQprepare()
Linux Kernel copy_from_user(), kfree_s()
Mac OS X _FREE_ZONE(), copyin()
ODBC SQLPrepareA(), SQLPrepareUNIX(), SQLPrepareW()
OpenSSL CRYPTO_malloc(), OPENSSL_cleanse()
Qt qMemCopy(), qMemSet()
Win32 BytesToUnicode(), StrNCatA(), StrNCatW(), wcsnlen()

Note that classes Addition Overflow of Size, Multiplication Overflow of Size, Subtraction Underflow of Size and Truncation of Size all have the same set of triggering functions.

Note

This is a "taint+dp" warning class: warnings of this class undergo a dedicated refinement phase that cannot be disabled. One consequence of this is that reporting exhibits some degree of unavoidable nondeterminism. If result stability is important to you, you may wish to avoid enabling this class.

In issuing a warning of this class, CodeSonar does not take into account any constraints on integer values that are imposed before the beginning of the warning's core path.

Relevant Configuration File Parameters

The following configuration file parameters affect checks for this warning class.

 

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