Re: [v4.9-rc4] dvb-usb/cinergyT2 NULL pointer dereference

Linus Torvalds
2016-11-08T18:42:14Z

On Sun, Nov 6, 2016 at 7:40 AM, Jörg Otte <jrg.otte@gmail.com> wrote:
> Since v4.9-rc4 I get following crash in dvb-usb-cinergyT2 module.

Looks like it's commit 5ef8ed0e5608f ("[media] cinergyT2-core: don't
do DMA on stack"), which movced the DMA data array from the stack to
the "private" pointer. In the process it also added serialization in
the form of "data_mutex", but and now it oopses on that mutex because
the private pointer is NULL.

It looks like the "->private" pointer is allocated in dvb_usb_adapter_init()

cinergyt2_usb_probe ->
dvb_usb_device_init ->
dvb_usb_init() ->
dvb_usb_adapter_init()

but the dvb_usb_init() function calls dvb_usb_device_power_ctrl()
(which calls the "power_ctrl" function, which is
cinergyt2_power_ctrl() for that drive) *before* it initializes the
private field.

Mauro, Patrick, could dvb_usb_adapter_init() be called earlier, perhaps?

Linus