On Tue, May 21, 2024 at 10:46 PM Andrey Konovalov <andreyknvl@xxxxxxxxx> wrote:
>
> On Tue, May 21, 2024 at 6:35 AM Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
> >
> > On Mon, 20 May 2024 at 22:59, <andrey.konovalov@xxxxxxxxx> wrote:
> > >
> > > From: Andrey Konovalov <andreyknvl@xxxxxxxxx>
> > >
> > > After commit 8fea0c8fda30 ("usb: core: hcd: Convert from tasklet to BH
> > > workqueue"), usb_giveback_urb_bh() runs in the BH workqueue with
> > > interrupts enabled.
> > >
> > > Thus, the remote coverage collection section in usb_giveback_urb_bh()->
> > > __usb_hcd_giveback_urb() might be interrupted, and the interrupt handler
> > > might invoke __usb_hcd_giveback_urb() again.
> > >
> > > This breaks KCOV, as it does not support nested remote coverage collection
> > > sections within the same context (neither in task nor in softirq).
> > >
> > > Update kcov_remote_start/stop_usb_softirq() to disable interrupts for the
> > > duration of the coverage collection section to avoid nested sections in
> > > the softirq context (in addition to such in the task context, which are
> > > already handled).
> >
> > Besides the issue pointed by the test robot:
> >
> > Acked-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> >
> > Thanks for fixing this.
>
> Thanks for the ack!
>
> > This section of code does not rely on reentrancy, right? E.g. one
> > callback won't wait for completion of another callback?
>
> I think all should be good. Before the BH workqueue change, the code
> ran with interrupts disabled.
>
> > At some point we started seeing lots of "remote cover enable write
> > trace failed (errno 17)" errors while running syzkaller. Can these
> > errors be caused by this issue?
>
> This looks like a different issue. I also noticed this when I tried
> running a log with a bunch of USB programs via syz-execprog. Not sure
> why this happens, but I still see it with this patch applied.
For the record:
https://lore.kernel.org/all/20240611133229.527822-1-nogikh@xxxxxxxxxx/
should address that problem.
--
Aleksandr
>
> Thanks!
>
