access denied error from WriteFile to physical disk, win7 - winapi

Question

I am trying to write some data to an SD card from a specific physical sector. I received a code to do this from a company and they say it works ok on windows-xp. This is the same case with WriteFile error #5 "denied access" under win Vista/seven
Here is the part writing the data to SD card (in my cae drv value is 'F'). Reading from others, I added locking and dismont but the lock fails (and dismount too). I'm not so familiar with windows programming. Can anybody tell me what's wrong in this code? Thanks for any help. (BTW I;m locking 3GiB)
u32 HDD_write(u8 drv, u32 SecAddr, u32 blocks, u8 *buf)
{
u32 ret = 0;
u32 ldistanceLow, ldistanceHigh, dwpointer, bytestoread, numread;
char cur_drv[100];
HANDLE g_hDevice;
sprintf(cur_drv, "\\\\.\\%c:",drv); // , (u32)drv);
g_hDevice = CreateFile(cur_drv, GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
if(g_hDevice == INVALID_HANDLE_VALUE)
return 0;
// lock and dismount
ret = LockFile(g_hDevice, 0, 0, 3 * 1023 * 1023 * 1023, 0);
printf("ret = %d", ret);
DeviceIoControl(g_hDevice, FSCTL_DISMOUNT_VOLUME, NULL, 0, NULL, 0, NULL, NULL);
printf("error = %d", GetLastError());
ldistanceLow = SecAddr << 9;
ldistanceHigh = SecAddr >> (32-9);
dwpointer = SetFilePointer(g_hDevice, ldistanceLow, (long *)&ldistanceHigh, FILE_BEGIN);
if(dwpointer != 0xFFFFFFFF) {
bytestoread = blocks * 512;
ret = WriteFile(g_hDevice, buf, bytestoread, (unsigned long *)&numread, NULL);
if(ret) ret = 1;
else {
ret = 0;
printf("error = %d", GetLastError());
}
}
CloseHandle(g_hDevice);
return ret;
}

Answer 1

I solved this problem several days ago and forgot to check my question here.
This is the code I used. We need GENERIC_READ also for block device when creating the file (for partitioned disk). and the key was dismount first and then lock.
u32 HDD_write(u8 drv, u32 SecAddr, u32 blocks, u8 *buf) {
u32 ret = 0;
u32 ldistanceLow, ldistanceHigh, dwpointer, bytestoread, numread;
char cur_drv[100];
HANDLE g_hDevice;
DWORD status;
//sprintf(cur_drv, "\\\\.\\PhysicalDrive%d", drv);
sprintf(cur_drv, "\\\\.\\%c:",drv);
g_hDevice = CreateFile(cur_drv, GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
if(g_hDevice == INVALID_HANDLE_VALUE)
return 0;
// dismout and lock added by ckim
if (!DeviceIoControl(g_hDevice, FSCTL_DISMOUNT_VOLUME,
NULL, 0, NULL, 0, &status, NULL))
{
DWORD err = GetLastError();
printf("Error %d attempting to dismount volume, error code\n",err);
}
// lock volume
if (!DeviceIoControl(g_hDevice, FSCTL_LOCK_VOLUME,
NULL, 0, NULL, 0, &status, NULL))
{
printf("Error %d attempting to lock device\n", GetLastError());
}
ldistanceLow = SecAddr << 9;
ldistanceHigh = SecAddr >> (32-9);
dwpointer = SetFilePointer(g_hDevice, ldistanceLow, (long *)&ldistanceHigh, FILE_BEGIN);
if(dwpointer != 0xFFFFFFFF) {
bytestoread = blocks * 512;
ret = WriteFile(g_hDevice, buf, bytestoread, (unsigned long *)&numread, NULL);
if(ret) ret = 1;
else {
ret = 0;
printf("error = %d", GetLastError());
}
}
CloseHandle(g_hDevice);
return ret;
}