Andrey Karpov

Mar 31 2017

Tags:

#Cpp #Security

Weaknesses detected by PVS-Studio this week: episode N4

• For those who are not familiar with PVS-Studio tool
• Weaknesses
• Miscellaneous errors
• Conclusion

We decided to search and fix potential vulnerabilities in various projects. You can call this as you wish - some kind of help to open source projects; a method of promotion or testing of the analyzer. Another way to see it as a way to attract attention to the reliability and quality of the code. In fact, the way to name these posts does not really matter - we just like doing it. This is our little hobby. So, let us have a look at our findings in the code of various projects this week - we had some time to make fixes and suggest looking at them.

For those who are not familiar with PVS-Studio tool

PVS-Studio is a tool that detects a large number of types of vulnerabilities and errors in the code. It performs static analysis and points to code fragments that are likely to contain errors. The best effect is achieved when the static analysis is performed regularly. Ideologically, the analyzer warnings are similar to the compiler warnings. However, unlike compilers, PVS-Studio can perform deeper and more versatile code analysis. This enables it to detect errors, even in compilers: GCC; LLVM 1, 2, 3; Roslyn.

The tool supports the analysis of C, C++ and C#; works under Windows and Linux. The analyzer can be integrated as a Visual Studio plug-in.

We suggest the following materials for further investigation of the tool:

• It is available on YouTube (47 min.) in the video format.
• Articles about checked open source projects.
• PVS-Studio: searching software weaknesses.

Weaknesses

In this section we show those defects that fall under the CWE classification and are potential vulnerabilities in their core. Of course, not all weaknesses are really threatening for a project, but we wanted to show that our tool is able to detect them.

1. CryEngine V. CWE-806 (Buffer Access Using Size of Source Buffer)

V512 A call of the 'memcpy' function will lead to underflow of the buffer 'hashableData'. GeomCacheRenderNode.cpp 285

void CGeomCacheRenderNode::Render(....)
{
  ....
  CREGeomCache* pCREGeomCache = iter->second.m_pRenderElement;
  ....
  uint8 hashableData[] =
  {
   0, 0, 0, 0, 0, 0, 0, 0,
   (uint8)std::distance(pCREGeomCache->....->begin(), &meshData),
   (uint8)std::distance(meshData....->....begin(), &chunk),
   (uint8)std::distance(meshData.m_instances.begin(), &instance)
  };

  memcpy(hashableData,pCREGeomCache,sizeof(pCREGeomCache)); // <=
  ....
}

2. CryEngine V. CWE-467 (Use of sizeof() on a Pointer Type)

V568 It's odd that 'sizeof()' operator evaluates the size of a pointer to a class, but not the size of the 'this' class object. ClipVolumeManager.cpp 145

void
CClipVolumeManager::GetMemoryUsage(class ICrySizer* pSizer) const
{
  pSizer->AddObject(this, sizeof(this));
  for (size_t i = 0; i < m_ClipVolumes.size(); ++i)
    pSizer->AddObject(m_ClipVolumes[i].m_pVolume);
}

3. CryEngine V. CWE-571 (Expression is Always True)

V501 There are identical sub-expressions to the left and to the right of the '==' operator: bActive == bActive LightEntity.h 124

void SetActive(bool bActive)
{
  if (bActive == bActive)
    return;

  m_bActive = bActive;
  OnResetState();
}

4. CryEngine V. CWE-476 (NULL Pointer Dereference)

V595 The 'pTrack' pointer was utilized before it was verified against nullptr. Check lines: 60, 61. AudioNode.cpp 60

void CAudioNode::Animate(SAnimContext& animContext)
{
  ....
  const bool bMuted = gEnv->IsEditor() && (pTrack->GetFlags() &
    IAnimTrack::eAnimTrackFlags_Muted);
  if (!pTrack || pTrack->GetNumKeys() == 0 ||
       pTrack->GetFlags() & IAnimTrack::eAnimTrackFlags_Disabled)
  {
    continue;
  }
  ....
}

5. CryEngine V. CWE-688 (Function Call With Incorrect Variable or Reference as Argument)

V549 The first argument of 'memcpy' function is equal to the second argument. ObjectsTree_Serialize.cpp 1135

void COctreeNode::LoadSingleObject(....)
{
  ....
  float* pAuxDataDst = pObj->GetAuxSerializationDataPtr(....);
  const float* pAuxDataSrc = StepData<float>(....);
  memcpy(pAuxDataDst, pAuxDataDst, min(....) * sizeof(float));
  ....
}

6. LLVM. CWE-476 (NULL Pointer Dereference)

V595 The 'DIExpr' pointer was utilized before it was verified against nullptr. Check lines: 949, 950. codeviewdebug.cpp 949

void CodeViewDebug::collectVariableInfo(const DISubprogram *SP) {
  ....
  const DIExpression *DIExpr = DVInst->getDebugExpression();
  bool IsSubfield = false;
  unsigned StructOffset = 0;

  // Handle fragments.
  auto Fragment = DIExpr->getFragmentInfo();   // <=
  if (DIExpr && Fragment) {                    // <=
    IsSubfield = true;
    StructOffset = Fragment->OffsetInBits / 8;
  } else if (DIExpr && DIExpr->getNumElements() > 0) {
    continue; // Ignore unrecognized exprs.
  }
  ....
}

Bug Report: https://bugs.llvm.org/show_bug.cgi?id=32430

7. LLVM. CWE-476 (NULL Pointer Dereference)

V595 The 'Initializer' pointer was utilized before it was verified against nullptr. Check lines: 335, 338. semaoverload.cpp 335

NarrowingKind
StandardConversionSequence::getNarrowingKind(....) const {
  ....
  const Expr *Initializer = IgnoreNarrowingConversion(Converted);

  if (Initializer->isValueDependent()) // <=
    return NK_Dependent_Narrowing;

  if (Initializer &&                   // <=
      Initializer->isIntegerConstantExpr(IntConstantValue, Ctx)){
  ....
}

Bug Report: https://bugs.llvm.org/show_bug.cgi?id=32447

8. RPCS3. CWE-570 (Expression is Always False)

V547 Expression 'sock < 0' is always false. Unsigned type value is never < 0. sys_net.cpp 695

#ifdef _WIN32
  using socket_t = SOCKET;
#else
  using socket_t = int;
#endif
s32 socket(s32 family, s32 type, s32 protocol)
{
  ....
  socket_t sock = ::socket(family, type, protocol);

  if (sock < 0)
  {
    libnet.error("socket()....", get_errno() = get_last_error());
    return -1;
  }
  ....
}

Pull Request: https://github.com/RPCS3/rpcs3/pull/2543

Miscellaneous errors

1. CoreCLR

V778 Two similar code fragments were found. Perhaps, this is a typo and 'IMAGE_LOADED_FOR_INTROSPECTION' variable should be used instead of 'IMAGE_LOADED'. cee_dac peimage.cpp 811

void PEImage::EnumMemoryRegions(CLRDataEnumMemoryFlags flags)
{
  ....
  if (m_pLayouts[IMAGE_LOADED].IsValid() &&
      m_pLayouts[IMAGE_LOADED]!=NULL)
    m_pLayouts[IMAGE_LOADED]->EnumMemoryRegions(flags);

  if (m_pLayouts[IMAGE_LOADED_FOR_INTROSPECTION].IsValid() &&
      m_pLayouts[IMAGE_LOADED]!=NULL)                   // <=
    m_pLayouts[IMAGE_LOADED_FOR_INTROSPECTION]->
      EnumMemoryRegions(flags);
}

Pull Request: https://github.com/dotnet/coreclr/pull/10450

2. CoreCLR

V778 Two similar code fragments were found. Perhaps, this is a typo and 'weight2' variable should be used instead of 'weight1'. clrjit lclvars.cpp 2702

int __cdecl Compiler::RefCntCmp(const void* op1, const void* op2)
{
  ....
  if (weight1)
  {
    ....
    if (varTypeIsGC(dsc1->TypeGet()))
    {
      weight1 += BB_UNITY_WEIGHT / 2;
    }
    if (dsc1->lvRegister)
    {
      weight1 += BB_UNITY_WEIGHT / 2;
    }
  }

  if (weight1)
  {
    ....
    if (varTypeIsGC(dsc2->TypeGet()))
    {
      weight1 += BB_UNITY_WEIGHT / 2;  // <=
    }
    if (dsc2->lvRegister)
    {
      weight2 += BB_UNITY_WEIGHT / 2;
    }
  }
  ....
}

Pull Request: https://github.com/dotnet/coreclr/pull/10450

3. CoreCLR

V778 Two similar code fragments were found. Perhaps, this is a typo and 'g_szBuf_ProperName' variable should be used instead of 'g_szBuf_UnquotedProperName'. ildasm dasm.cpp 486

void Uninit()
{
  ....
  if (g_szBuf_UnquotedProperName != NULL)
  {
    SDELETE(g_szBuf_UnquotedProperName);
  }
  if (g_szBuf_UnquotedProperName != NULL)  // <=
  {
    SDELETE(g_szBuf_ProperName);
  }
  ....
}

Pull Request: https://github.com/dotnet/coreclr/pull/10450

4. LLVM

V778 Two similar code fragments were found. Perhaps, this is a typo and 'FS' variable should be used instead of 'TS'. hexagonearlyifconv.cpp 549

bool HexagonEarlyIfConversion::isProfitable(....) const
{
  ....
  unsigned TS = 0, FS = 0, Spare = 0;
  if (FP.TrueB) {
    TS = std::distance(FP.TrueB->begin(),
      FP.TrueB->getFirstTerminator());
    if (TS < HEXAGON_PACKET_SIZE)
      Spare += HEXAGON_PACKET_SIZE-TS;     // <=
  }
  if (FP.FalseB) {
    FS = std::distance(FP.FalseB->begin(),
      FP.FalseB->getFirstTerminator());
    if (FS < HEXAGON_PACKET_SIZE)
      Spare += HEXAGON_PACKET_SIZE-TS;     // <=
  }
  unsigned TotalIn = TS+FS;
  ....
}

Bug Report: https://bugs.llvm.org/show_bug.cgi?id=32480

Conclusion

We suggest downloading PVS-Studio analyzer and trying to check your project:

• Download PVS-Studio for Windows.
• Download PVS-Studio for Linux.

To remove the restrictions of a demo version, you can contact us and we will provide a temporary license key for you.

For a quick introduction to the analyzer, you can use the tools, tracking the runs of the compiler and collect all the necessary information for the analysis. See the description of the utilities CLMonitoring and pvs-studio-analyzer. If you are working with a classic type of project in Visual Studio, everything is much simpler: you should just choose in PVS-Studio menu a command "Check Solution".

#Cpp #Security

0

0

0

0

SHARE

Tags:

#Cpp #Security

We can email you a selection of our best articles once a month