On Mon, Mar 23, 2015 at 04:00:37PM -0700, Badhri Jagan Sridharan wrote:
> > Do you really see some udc drivers call it after composite_unbind is
> > called? If it is, you may add dump_stack() to track that error.
> >
> > Besides this, function suspended_show is needed to add cdev NULL pointer
> > checking.
>
> We see this happening occasionally in *not yet* upstreamed UDC
> code of some vendors (Yes, disconnect being called after unbind)
Does it a spurious interrupt?
I guess if you add struct usb_gadget_driver NULL pointer check check, it
will not occur:
if (you_udc->driver)
you_udc->driver->disconnect(&you_udc->gadget);
> After reviewing the entire composite.c file, I did notice that
> none of the functions check for NULL pointer when cdev is
> obtained from get_gadget_data.
> Is crashing/bringing down the whole kernel intentionally
> left to happen ?
Hmm, I don't think, the design may think it never occurs.
> Isn't printing a WARN/ERROR msg and
> returning not the preferable approach ?
I think BUG_ON is more suitable, let's see Felipe's comment.
>
> On 03/22/2015 12:43 AM, Peter Chen wrote:
> >On Fri, Mar 20, 2015 at 04:40:52PM -0700, Badhri Jagan Sridharan wrote:
> >>Added a safety net to make sure that
> >>composite_disconnect does not end up disconneting
> >>a NULL device. Prevents NULL pointer crash.
> >>
> >>Signed-off-by: Badhri Jagan Sridharan <Badhri@xxxxxxxxxx>
> >>---
> >> drivers/usb/gadget/composite.c | 5 +++++
> >> 1 file changed, 5 insertions(+)
> >>
> >>diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
> >>index 13adfd1..90b37bd 100644
> >>--- a/drivers/usb/gadget/composite.c
> >>+++ b/drivers/usb/gadget/composite.c
> >>@@ -1823,6 +1823,11 @@ void composite_disconnect(struct usb_gadget *gadget)
> >> struct usb_composite_dev *cdev = get_gadget_data(gadget);
> >> unsigned long flags;
> >>
> >>+ if (!cdev) {
> >>+ WARN(1, "Trying to disconnect a NULL composite device\n");
> >>+ return;
> >>+ }
> >>+
> >
> >Do you really see some udc drivers call it after composite_unbind is
> >called? If it is, you may add dump_stack() to track that error.
> >
> >Besides this, function suspended_show is needed to add cdev NULL pointer
> >checking.
> >
> >> /* REVISIT: should we have config and device level
> >> * disconnect callbacks?
> >> */
> >>--
> >>2.2.0.rc0.207.ga3a616c
> >>
> >>--
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> >
--
Best Regards,
Peter Chen
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