On 7 May 2018 at 10:44, Gerd Hoffmann <[email protected]> wrote:
> From: Bandan Das <[email protected]>
>
> CID 1390578: In usb_mtp_write_metadata, parent can never be NULL but
> just in case, add an assert
> CID 1390592: Check for o->format only if o !=NULL
> CID 1390604: Check s->data_out != NULL in usb_mtp_handle_data
> @@ -1838,7 +1838,7 @@ static void usb_mtp_handle_data(USBDevice *dev,
> USBPacket *p)
> p->status = USB_RET_STALL;
> return;
> }
> - if (s->data_out && !s->data_out->first) {
> + if ((s->data_out != NULL) && !s->data_out->first) {
> container_type = TYPE_DATA;
> } else {
> usb_packet_copy(p, &container, sizeof(container));
> --
I just noticed this, but this isn't actually changing the logic
in this function: "s->data_out" and "s->data_out != NULL" are
exactly the same test. So this won't change CID 1390604.
Looking back at my previous email on this, it looks like I
managed to completely misinterpret the code and/or what
coverity is talking about, which is probably the source of
the confusion. Let me try again...
In the function usb_mtp_handle_data() EP_DATA_OUT case, we have:
(1) a check for whether s->data_out is NULL, which implies
that it might be NULL sometimes
(2) some time later, a call to usb_mtp_get_data() which is
not protected by a test for whether s->data_out is NULL
and if s->data_out is NULL at point (2) then usb_mtp_get_data()
will crash.
Obviously the code path that goes through "containe_type = TYPE_DATA"
must have s->data_out being non-NULL. But in the else branch of
that, can the container_type we get via usb_packet_copy() ever
be TYPE_DATA ? (It's not clear to me whether that comes from
a trusted or untrusted source.)
If this is a "can't happen" situation we can mark it as a false
positive in coverity.
thanks
-- PMM
