linux-kernel - Re: [PATCH v3] media: mxl111sf: change mutex

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Date:   Wed, 15 Sep 2021 17:40:01 +0100
From:   Sean Young <sean@...s.org>
To:     Pavel Skripkin <paskripkin@...il.com>
Cc:     mkrufky@...uxtv.org, mchehab@...nel.org, crope@....fi,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzbot+5ca0bf339f13c4243001@...kaller.appspotmail.com
Subject: Re: [PATCH v3] media: mxl111sf: change mutex_init() location

On Sun, Sep 12, 2021 at 06:49:52PM +0300, Pavel Skripkin wrote:
> On 8/19/21 13:42, 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_* devices call mxl111sf_ctrl_msg() in ->frontend_attach()
> > internally we need to initialize state->msg_lock before
> > frontend_attach(). To achieve it, ->probe() call added to all mxl111sf_*
> > devices, which will simply initiaize mutex.
> > 
> > Reported-and-tested-by: syzbot+5ca0bf339f13c4243001@...kaller.appspotmail.com
> > Fixes: 8572211842af ("[media] mxl111sf: convert to new DVB USB")
> > Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
> 
> Hi, Sean!
> 
> Did you have a chance to review this patch? Thank you :)

Sorry during the merge window (from -rc6 to -rc1) I don't tend to look
at patches. Looks good to me, I'll merge it.

Thanks

Sean