Uninitialized Read Error - c++

Question

i have written a method to get all process id's inside a c++ project.
Int CProcessHelper::GetAllPIDs(const char *processName, _STL_NAMESPACE_::vector<DWORD> &pids)
{
HANDLE hProcessSnap;
PROCESSENTRY32 pe32;
HANDLE hProcess;
BOOL bContinue;
pids.clear();
// Take a snapshot of all processes in the system.
hProcessSnap = CreateToolhelp32Snapshot( TH32CS_SNAPPROCESS, 0 );
if( hProcessSnap == INVALID_HANDLE_VALUE )
{
return 0;
}
// Set the size of the structure before using it.
pe32.dwSize = sizeof( PROCESSENTRY32 );
// Retrieve information about the first process,
// and exit if unsuccessful
bContinue = Process32First( hProcessSnap, &pe32 );
while(bContinue)
{
hProcess = OpenProcess(PROCESS_QUERY_INFORMATION|PROCESS_VM_READ, FALSE, pe32.th32ProcessID);
if( hProcess != NULL )
{
TCHAR szModName[MAX_PATH];
// Get the full path to the module's file.
if(GetModuleFileNameEx( hProcess, NULL, szModName,
sizeof(szModName)))
{
char *ptr = strrchr(szModName, '\\');
if( (ptr && stricmp(ptr+1, processName) == 0) ||
stricmp(szModName, processName) == 0)
{
pids.push_back(pe32.th32ProcessID);
/*CloseHandle( hProcess );
pid = pe32.th32ProcessID;
break;*/
}
}
CloseHandle( hProcess );
}
bContinue = Process32Next( hProcessSnap, &pe32 );
}
CloseHandle( hProcessSnap );
return (int) pids.size();
}
When i run this code under Dr Memory, i am getting following "Uninitialized Read" errors:
Uninitialized Read Error 1
at this line:
if(GetModuleFileNameEx( hProcess, NULL, szModName,
sizeof(szModName)))
2nd error is :
Uninitialized Read Error 2
at this line -
bContinue = Process32First( hProcessSnap, &pe32 );
i am not getting by Dr Memory reporting me these errors. Are these only false positive errors?
Please help me to identify which part is uninitialized here.
If you look at the attached Dr Memory error screenshot carefully, you will notice that both the errors have call to the
KERNELBASE.dll!WideCharToMultiByte
Since i am using TCHAR(1.e of char type, rather then of WCHAR type(wide char)) for szFileName var.
TCHAR szModName[MAX_PATH];
I am not getting why it is calling WideCharToMultiByte() method as i am using a method which accept char type rather then a wide char type.

Answer 1

hProcess = OpenProcess(PROCESS_QUERY_INFORMATION | PROCESS_VM_READ, FALSE, pe32.th32ProcessID);
pe32.th32ProcessID is not set yet, it's uninitialized memory. OpenProcess() is also not needed for your purpose.
if (GetModuleFileNameEx(hProcess, NULL, szModName, sizeof(szModName)))
this function is unnecessary, the executable name is exposed by the PROCESSENTRY32 structure. In addition, the last argument should use strlen, not sizeof because you want number of characters not size of buffer.
There are other issues with this code as well, rather than trying to reinvent the wheel, MSDN has a complete commented source code for doing what you want to do using the ToolHelp32Snapshot collection of functions, you can find it here.
Here is a concise example I have modified to fit your needs without any problems:
#include <windows.h>
#include <iostream>
#include <vector>
#include <TlHelp32.h>
#include <Psapi.h>
int GetAllPIDs(const char* processName, std::vector<DWORD>& pids)
{
HANDLE hSnap = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
if (hSnap != INVALID_HANDLE_VALUE)
{
PROCESSENTRY32 procEntry;
procEntry.dwSize = sizeof(procEntry);
if (Process32First(hSnap, &procEntry))
{
do
{
if (!_stricmp(procEntry.szExeFile, processName))
{
pids.push_back(procEntry.th32ProcessID);
}
} while (Process32Next(hSnap, &procEntry));
}
}
CloseHandle(hSnap);
return (int)pids.size();
}
int main()
{
std::vector<DWORD> piddies;
GetAllPIDs("calc.exe", piddies);
for (auto p : piddies)
{
std::cout << "0x" << std::hex << p << std::endl;
}
std::getchar();
return 0;
}