Re: [GIT PULL for v4.6-rc1] media updates

From: Linus Torvalds
Date: Tue May 03 2016 - 17:53:38 EST

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.