Wim Osterholt <wim@xxxxxxxxxxxxxx> writes: > On Mon, Nov 21, 2016 at 02:19:32PM +0100, Oliver Neukum wrote: > >> I don't understand it, bit please test the attached patch >> with dynamic debugging for cdc-acm and the kernel log level >> at maximum. > >> diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c >> index 6895f9e..f03b5db 100644 >> --- a/drivers/usb/class/cdc-acm.c >> +++ b/drivers/usb/class/cdc-acm.c >> @@ -1188,6 +1188,12 @@ static int acm_probe(struct usb_interface *intf, >> >> cdc_parse_cdc_header(&h, intf, buffer, buflen); >> union_header = h.usb_cdc_union_desc; >> + >> + dev_dbg(&intf->dev, "Parsed device header\n"); >> + dev_dbg(&intf->dev, "Union descriptor %p\n", h.usb_cdc_union_desc); >> + dev_dbg(&intf->dev, "ACM descriptor %p\n", h.usb_cdc_acm_descriptor); >> + dev_dbg(&intf->dev, "Country descriptor %p\n", h.usb_cdc_country_functional_desc); >> + >> cmgmd = h.usb_cdc_call_mgmt_descriptor; >> if (cmgmd) >> call_intf_num = cmgmd->bDataInterface; > > > On kernel 4.8.8 this crashes hard and produces over a serial link: Huh? That device shouldn't ever enter that code path AFAICS. Unless.... you wouldn't happen to add a dynamic entry for this device, would you? What's the output of cat /sys/bus/usb/drivers/cdc_acm/new_id ? We should probably survive it, but I think the current acm_probe() is going to barf hard on the last data interface, if probed without the default NO_UNION_NORMAL quirk. cdc_parse_cdc_header() will happily parse all the functional descriptors, including the union pointing to interfaces 0 and 1. I might be missing it, but I cannot see any sanity check verifying that the currently probed interface is actually part of the set of interfaces pointed to by the union. There is a sanity check for the availability of the data interface, but there is none for the control interface (the assumption of course that that's the interface we're probing). I think we need a bit more sanity checking of the union. This is likely a generic problem for any CDC driver, so it is worth considering adding a shared function for that. And all this fails to explain anything if you didn't add the device dynamically, of course... Bjørn -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
