VGDrvCommonIoCtl may be potentially dereferencing a null pointer on pcbDataReturned

[ColinIanKing]

Function VGDrvCommonIoCtl in src/VBox/Additions/common/VBoxGuest/VBoxGuest.cpp is checking to see if pcbDataReturned is NULL and then setting it to zero, thus the code assumes there is a potential for the pointer to be NULL. However, later in the function we have:

            case VBOXGUEST_IOCTL_GUEST_CAPS_ACQUIRE:
                CHECKRET_SIZE("GUEST_CAPS_ACQUIRE", sizeof(VBoxGuestCapsAquire));
                rc = vgdrvIoCtl_GuestCapsAcquire(pDevExt, pSession, (VBoxGuestCapsAquire *)pvData);
                *pcbDataReturned = sizeof(VBoxGuestCapsAquire);
                break;

and this dereferencing the pointer that could potentially be zero.

[Frank Mehnert]

False positive. It can indeed happen that VGDrvCommonIoCtl() is called with pcbDataReturned = NULL but it's that parameter is never NULL for iFunction=VBOXGUEST_IOCTL_GUEST_CAPS_ACQUIRE. I admit that this is not obvious and that this is bad style but it's still not a bug and it's not worth to open a ticket.

[Socratis]

An advice if I may to "ColinIanKing"...
You can have the same effect if you post an e-mail to the VirtualBox developers' mailing list, without the need to open a ticket.