> From: "Theo de Raadt" <dera...@openbsd.org>
> cc: Patrick Wildt <patr...@blueri.se>
> Comments: In-reply-to Mikolaj Kucharski <miko...@kucharski.name>
> message dated "Mon, 13 Apr 2020 18:55:37 -0000."
> Content-Type: text/plain; charset="us-ascii"
> Content-ID: <61132.158680562...@cvs.openbsd.org>
> Date: Mon, 13 Apr 2020 13:20:27 -0600
>
> Mikolaj Kucharski <miko...@kucharski.name> wrote:
>
> > On Mon, Apr 13, 2020 at 12:44:54PM -0600, Theo de Raadt wrote:
> > > Then you need to look at why this crazy value is composed here in this
> > > loop:
> > >
> > > actlen = 0;
> > > for (sqtd = ex->sqtdstart; sqtd != NULL; sqtd = sqtd->nextqtd) {
> > > usb_syncmem(&sqtd->dma, sqtd->offs, sizeof(sqtd->qtd),
> > > BUS_DMASYNC_POSTWRITE | BUS_DMASYNC_POSTREAD);
> > > nstatus = letoh32(sqtd->qtd.qtd_status);
> > > if (nstatus & EHCI_QTD_ACTIVE)
> > > break;
> > >
> > > status = nstatus;
> > > /* halt is ok if descriptor is last, and complete */
> > > if (sqtd->qtd.qtd_next == htole32(EHCI_LINK_TERMINATE) &&
> > > EHCI_QTD_GET_BYTES(status) == 0)
> > > status &= ~EHCI_QTD_HALTED;
> > > if (EHCI_QTD_GET_PID(status) != EHCI_QTD_PID_SETUP)
> > > actlen += sqtd->len - EHCI_QTD_GET_BYTES(status);
> > > }
> >
> > But I just described that in one of my previous emails few minutes ago.
> >
> > In my diff I'm using second loop of the same code, but I guess I can
> > provide more surgurucal diff to be more explicit. What I wrote in my
> > previous email can be written also as follows:
> >
> > actlen += sqtd->len - EHCI_QTD_GET_BYTES(status);
> >
> > In above equation, on first for loop iteration:
> >
> > actlen is 0
> > EHCI_QTD_GET_BYTES(status) is 16000
> > sqtd->len is 8
> >
> > actlen += 8 - 1600;
> >
> > Which results of actlen being 4294951304, from that moment we are
> > heading to kernel panic.
>
> Then next step is to figure out why the sqtd is incoherent.
I actually suspect that the 16000 here is bogus. Can you print the
status (full 32 bits) of that particular QTD?
