Re: [PATCH] media: mxl111sf: change mutex_init() location

[Pavel Skripkin]

On 8/15/21 11:37 AM, Sean Young wrote:
> On Sat, Jul 31, 2021 at 12:38:29AM +0300, Pavel Skripkin wrote:
> > Syzbot reported, that mxl111sf_ctrl_msg() uses uninitialized
> > mutex. The problem was in wrong mutex_init() location.
> >
> > Previous mutex_init(&state->msg_lock) call was in ->init() function, but
> > dvb_usbv2_init() has this order of calls:
> >
> > 	dvb_usbv2_init()
> > 	  dvb_usbv2_adapter_init()
> > 	    dvb_usbv2_adapter_frontend_init()
> > 	      props->frontend_attach()
> >
> > 	  props->init()
> >
> > Since mxl111sf_frontend_attach_atsc_mh() calls mxl111sf_ctrl_msg()
> > internally we need to initialize state->msg_lock in it to make lockdep
> > happy.
>
> What about the other frontends like mxl111sf_frontend_attach_dvbt? They
> no longer initialize the mutex.
Good point. I see, that all other frontends also call 
mxl111sf_ctrl_msg() inside ->frontend_attach() call.

I think, that fixing dvb-usb core is not good idea, so, I will add 
mutex_init() call inside all frontends, which use mxl111sf_init().

What do you think about it?


With regards,
Pavel Skripkin