GetProcessMemoryInfo failed with error 6 Handle is invalid - c++

Question

I'm trying to get the list of processes running in the system using C++. I use the functions available in the Windows API (like OpenProcess & CreateToolhelp32Snapshot ) to get it done.
The problem is that the code works fine for most of the processes, but couldn't get the memory info for crucial system processes alone, I have given the seDebugPrivilege also and have run the program as administrator only.
I get the output like
File Name PID Memory Used
winlogon.exe 1248 2432 KB
fontdrvhost.exe 1308
WARNING: GetProcessMemoryInfo failed with error 6 (The handle is invalid)
dwm.exe 1384
WARNING: GetProcessMemoryInfo failed with error 6 (The handle is invalid)
svchost.exe 1448 4744 KB
My code is :
BOOL GetProcessList( )
{
HANDLE hProcessSnap;
HANDLE hProcess;
HANDLE hToken;
PROCESSENTRY32 pe32;
DWORD dwPriorityClass;
PROCESS_MEMORY_COUNTERS pmc;
hProcessSnap = CreateToolhelp32Snapshot( TH32CS_SNAPPROCESS, 0 );
if( hProcessSnap == INVALID_HANDLE_VALUE )
{
char err[]="CreateToolhelp32Snapshot (of processes)";
printError( err );
return( FALSE );
}
pe32.dwSize = sizeof( PROCESSENTRY32 );
if( !Process32First( hProcessSnap, &pe32 ) )
{
char err[]="Process32First";
printError( err ); // show cause of failure
CloseHandle( hProcessSnap ); // clean the snapshot object
return( FALSE );
}
if(!OpenThreadToken(GetCurrentThread(), TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY, FALSE, &hToken))
{
if (GetLastError() == ERROR_NO_TOKEN)
{
if (!ImpersonateSelf(SecurityImpersonation))
return FALSE;
if(!OpenThreadToken(GetCurrentThread(), TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY, FALSE, &hToken)){
char err[]="OpenThreadToken";
printError( err );
return FALSE;
}
}
else
return FALSE;
}
SetPrivilege(hToken, SE_DEBUG_NAME, FALSE);
do
{
printf( "%-25s", pe32.szExeFile );
dwPriorityClass = 0;
SIZE_T dwMin, dwMax;
hProcess = OpenProcess( PROCESS_QUERY_LIMITED_INFORMATION , FALSE, pe32.th32ProcessID );
printf("%-10d", pe32.th32ProcessID );
if(GetProcessMemoryInfo( hProcess, (PROCESS_MEMORY_COUNTERS *)&pmc, sizeof(pmc)))
{
printf( "%-10d KB", pmc.PagefileUsage/1024);
} else{
char err[]="GetProcessMemoryInfo";
printError( err );
}
printf("\n");
CloseHandle(hProcess);
}while( Process32Next( hProcessSnap, &pe32 ) );
CloseHandle( hProcessSnap );
return( TRUE );
}

Answer 1

To get this code to work, you have to change:
SetPrivilege(hToken, SE_DEBUG_NAME, FALSE)
to:
SetPrivilege(hToken, SE_DEBUG_NAME, TRUE)
As others have commented, to get this code to work properly, you have to:
check for and report all possible error conditions
release all resources when you are done, in this case release hToken (via CloseHandle()) and call revertToSelf() if needs be.
Other than that, it's a decent effort so thumbs up for that.
Link to SetPrivilege(), in case any future visitor needs it:
https://msdn.microsoft.com/en-us/library/windows/desktop/aa446619.aspx
Happy hacking.