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

Pavel Skripkin
2021-08-15T08:49:35Z

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