ReadProcessMemory _out_ bytesread - c++

Question

The program uses ReadProcessMemory to scan through chunks of memory for a certain value. Unfortunately when I call ReadProcessMemory I get error 299.
void update_memblock(MEMBLOCK *mb)
{
//variables
static unsigned char tempbuf[128*1024];
size_t bytes_left;
size_t total_read;
size_t bytes_to_read;
size_t bytes_read;
size_t sizeMem;
size_t MemoryBase;
bytes_left = mb->size;
total_read = 0;
while (bytes_left)
{
bytes_to_read = (bytes_left > sizeof(tempbuf)) ? sizeof(tempbuf) : bytes_left;
ReadProcessMemory(mb->hProc ,mb->addr + total_read,mb->buffer, bytes_to_read, (SIZE_T*)&bytes_read);
if (bytes_read != bytes_to_read)break;
memcpy(mb->buffer + total_read, tempbuf,bytes_read);
bytes_left -= bytes_read;
total_read += bytes_read;
}
mb->size = total_read;
}

Answer 1

Erorr Code 299 (0x12B) ERROR_PARTIAL_COPY
"Only part of a ReadProcessMemory or WriteProcessMemory request was completed"
You're receiving this error because you're trying to read memory from a page that isn't "allocated".
You want to use VirtualQueryEx() on each page of memory which yields a MEMORY_BASIC_INFORMATION structure, which contains 2 variables of note:
State: can be MEM_COMMIT, MEM_FREE or MEM_RESERVE
Protect: can be any of the Memory Protection Constants
You want to loop through all the pages of memory, call VirtualQueryEx() on them and skip any pages that are bad. I like to skip all pages/regions in which state != MEM_COMMIT and Protect == PAGE_NOACCESS
Here is a psuedo code example:
MEMORY_BASIC_INFORMATION mbi = { 0 };
while (LoopingThroughTheMemories.bat)
{
if (!VirtualQueryEx(hProc, currentMemoryAddress, &mbi, sizeof(mbi))) continue
if (mbi.State != MEM_COMMIT || mbi.Protect == PAGE_NOACCESS) continue;
//good mem region, do ReadProcessMemory() stuffs
}