Hi On 2016-05-03, Linus Torvalds wrote: > On Tue, May 3, 2016 at 2:38 PM, Stefan Lippers-Hollmann <s.l-h@xxxxxx> wrote: > > Hi > > [...] > >> Mauro Carvalho Chehab (95): > > [...] > >> [media] use v4l2_mc_usb_media_device_init() on most USB devices > > [...] > > > > This change, as part of v4.6-rc6-85-g1248ded, breaks two systems, each > > equipped with a TeVii s480 (dvb_usb_dw2102) DVB-S2 card, for me (kernel > > v4.5.3-rc1 is fine): > > From the oops it looks like the "->prev" pointer in one of the list > heads in 'mdev' is NULL. > > > [ 5.041915] BUG: unable to handle kernel NULL pointer dereference at (null) > > [ 5.041921] IP: [<ffffffffa0017b18>] media_gobj_create+0xb8/0x100 [media] > > I can't tell *which* list head it is, but it looks like there's a > missing call to media_device_init() which is what should have > initialized those list heads. > > Of course, maybe that list pointer got initialized but then > overwritten by NULL for some other reason. Just as a cross-check, this (incomplete, but au0828, cx231xx and em28xx aren't needed/ loaded on my system) crude revert avoids the problem for me on v4.6-rc6-113-g83858a7. --- a/drivers/media/usb/dvb-usb/dvb-usb-dvb.c +++ b/drivers/media/usb/dvb-usb/dvb-usb-dvb.c @@ -107,7 +107,15 @@ static int dvb_usb_media_device_init(str if (!mdev) return -ENOMEM; - media_device_usb_init(mdev, udev, d->desc->name); + mdev->dev = &udev->dev; + strlcpy(mdev->model, d->desc->name, sizeof(mdev->model)); + if (udev->serial) + strlcpy(mdev->serial, udev->serial, sizeof(mdev->serial)); + strcpy(mdev->bus_info, udev->devpath); + mdev->hw_revision = le16_to_cpu(udev->descriptor.bcdDevice); + mdev->driver_version = LINUX_VERSION_CODE; + + media_device_init(mdev); dvb_register_media_controller(&adap->dvb_adap, mdev); --- a/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c +++ b/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c @@ -412,7 +412,15 @@ static int dvb_usbv2_media_device_init(s if (!mdev) return -ENOMEM; - media_device_usb_init(mdev, udev, d->name); + mdev->dev = &udev->dev; + strlcpy(mdev->model, d->name, sizeof(mdev->model)); + if (udev->serial) + strlcpy(mdev->serial, udev->serial, sizeof(mdev->serial)); + strcpy(mdev->bus_info, udev->devpath); + mdev->hw_revision = le16_to_cpu(udev->descriptor.bcdDevice); + mdev->driver_version = LINUX_VERSION_CODE; + + media_device_init(mdev); dvb_register_media_controller(&adap->dvb_adap, mdev); While testing this, I also noticed that not just the dvb_usb based dvb_usb_dw2102 is affected, but that also the dvb_usb_v2 based rtl2832 triggers this Oops on its own (given that just reverting drivers/media/usb/dvb-usb/dvb-usb-dvb.c wasn't enough). Regards Stefan Lippers-Hollmann -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
