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

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

[Pavel Skripkin]

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.

Reported-and-tested-by: syzbot+5ca0bf339f13c4243001@syzkaller.appspotmail.com
Fixes: 8572211842af ("[media] mxl111sf: convert to new DVB USB")
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
---
 drivers/media/usb/dvb-usb-v2/mxl111sf.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/dvb-usb-v2/mxl111sf.c b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
index 7865fa0a8295..2e5663ffa7ce 100644
--- a/drivers/media/usb/dvb-usb-v2/mxl111sf.c
+++ b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
@@ -931,8 +931,6 @@ static int mxl111sf_init(struct dvb_usb_device *d)
 		  .len = sizeof(eeprom), .buf = eeprom },
 	};
 
-	mutex_init(&state->msg_lock);
-
 	ret = get_chip_info(state);
 	if (mxl_fail(ret))
 		pr_err("failed to get chip info during probe");
@@ -979,8 +977,12 @@ static int mxl111sf_frontend_attach_mh(struct dvb_usb_adapter *adap)
 static int mxl111sf_frontend_attach_atsc_mh(struct dvb_usb_adapter *adap)
 {
 	int ret;
+	struct mxl111sf_state *state = d_to_priv(adap_to_d(adap));
+
 	pr_debug("%s\n", __func__);
 
+	mutex_init(&state->msg_lock);
+
 	ret = mxl111sf_lgdt3305_frontend_attach(adap, 0);
 	if (ret < 0)
 		return ret;
-- 
2.32.0

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

[Sean Young]

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.

Thanks

Sean

> 
> Reported-and-tested-by: syzbot+5ca0bf339f13c4243001@syzkaller.appspotmail.com
> Fixes: 8572211842af ("[media] mxl111sf: convert to new DVB USB")
> Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
> ---
>  drivers/media/usb/dvb-usb-v2/mxl111sf.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/usb/dvb-usb-v2/mxl111sf.c b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
> index 7865fa0a8295..2e5663ffa7ce 100644
> --- a/drivers/media/usb/dvb-usb-v2/mxl111sf.c
> +++ b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
> @@ -931,8 +931,6 @@ static int mxl111sf_init(struct dvb_usb_device *d)
>  		  .len = sizeof(eeprom), .buf = eeprom },
>  	};
>  
> -	mutex_init(&state->msg_lock);
> -
>  	ret = get_chip_info(state);
>  	if (mxl_fail(ret))
>  		pr_err("failed to get chip info during probe");
> @@ -979,8 +977,12 @@ static int mxl111sf_frontend_attach_mh(struct dvb_usb_adapter *adap)
>  static int mxl111sf_frontend_attach_atsc_mh(struct dvb_usb_adapter *adap)
>  {
>  	int ret;
> +	struct mxl111sf_state *state = d_to_priv(adap_to_d(adap));
> +
>  	pr_debug("%s\n", __func__);
>  
> +	mutex_init(&state->msg_lock);
> +
>  	ret = mxl111sf_lgdt3305_frontend_attach(adap, 0);
>  	if (ret < 0)
>  		return ret;
> -- 
> 2.32.0

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

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

[Pavel Skripkin]

On 8/15/21 11:49 AM, Pavel Skripkin wrote:
> 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?
> 
> 


Something like this should work. Helper is just to not copy-paste code 
parts. Build tested against v5.14-rc5


diff --git a/drivers/media/usb/dvb-usb-v2/mxl111sf.c 
b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
index 7865fa0a8295..db1ad3815cd5 100644
--- a/drivers/media/usb/dvb-usb-v2/mxl111sf.c
+++ b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
@@ -49,6 +49,13 @@ MODULE_PARM_DESC(rfswitch, "force rf switch position 
(0=auto, 1=ext, 2=int).");

  DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nr);

+static inline void mxl111sf_init_msg_mutex(struct dvb_usb_adapter *adap)
+{
+	struct mxl111sf_state *state = d_to_priv(adap_to_d(adap));
+
+	mutex_init(&state->msg_lock);
+}
+
  int mxl111sf_ctrl_msg(struct mxl111sf_state *state,
  		      u8 cmd, u8 *wbuf, int wlen, u8 *rbuf, int rlen)
  {
@@ -931,8 +938,6 @@ static int mxl111sf_init(struct dvb_usb_device *d)
  		  .len = sizeof(eeprom), .buf = eeprom },
  	};

-	mutex_init(&state->msg_lock);
-
  	ret = get_chip_info(state);
  	if (mxl_fail(ret))
  		pr_err("failed to get chip info during probe");
@@ -963,16 +968,19 @@ static int mxl111sf_init(struct dvb_usb_device *d)

  static int mxl111sf_frontend_attach_dvbt(struct dvb_usb_adapter *adap)
  {
+	mxl111sf_init_msg_mutex(adap);
  	return mxl111sf_attach_demod(adap, 0);
  }

  static int mxl111sf_frontend_attach_atsc(struct dvb_usb_adapter *adap)
  {
+	mxl111sf_init_msg_mutex(adap);
  	return mxl111sf_lgdt3305_frontend_attach(adap, 0);
  }

  static int mxl111sf_frontend_attach_mh(struct dvb_usb_adapter *adap)
  {
+	mxl111sf_init_msg_mutex(adap);
  	return mxl111sf_lg2160_frontend_attach(adap, 0);
  }

@@ -981,6 +989,7 @@ static int mxl111sf_frontend_attach_atsc_mh(struct 
dvb_usb_adapter *adap)
  	int ret;
  	pr_debug("%s\n", __func__);

+	mxl111sf_init_msg_mutex(adap);
  	ret = mxl111sf_lgdt3305_frontend_attach(adap, 0);
  	if (ret < 0)
  		return ret;
@@ -1001,6 +1010,7 @@ static int mxl111sf_frontend_attach_mercury(struct 
dvb_usb_adapter *adap)
  	int ret;
  	pr_debug("%s\n", __func__);

+	mxl111sf_init_msg_mutex(adap);
  	ret = mxl111sf_lgdt3305_frontend_attach(adap, 0);
  	if (ret < 0)
  		return ret;
@@ -1021,6 +1031,7 @@ static int 
mxl111sf_frontend_attach_mercury_mh(struct dvb_usb_adapter *adap)
  	int ret;
  	pr_debug("%s\n", __func__);

+	mxl111sf_init_msg_mutex(adap);
  	ret = mxl111sf_attach_demod(adap, 0);
  	if (ret < 0)
  		return ret;



With regards,
Pavel Skripkin

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

[Sean Young]

On Sun, Aug 15, 2021 at 12:06:16PM +0300, Pavel Skripkin wrote:
> On 8/15/21 11:49 AM, Pavel Skripkin wrote:
> > 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?
> > 
> > 
> 
> 
> Something like this should work. Helper is just to not copy-paste code
> parts. Build tested against v5.14-rc5

How about creating a dvb_usb_device_properties probe function and
initializing the mutex init there?


Sean

> 
> 
> diff --git a/drivers/media/usb/dvb-usb-v2/mxl111sf.c
> b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
> index 7865fa0a8295..db1ad3815cd5 100644
> --- a/drivers/media/usb/dvb-usb-v2/mxl111sf.c
> +++ b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
> @@ -49,6 +49,13 @@ MODULE_PARM_DESC(rfswitch, "force rf switch position
> (0=auto, 1=ext, 2=int).");
> 
>  DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nr);
> 
> +static inline void mxl111sf_init_msg_mutex(struct dvb_usb_adapter *adap)
> +{
> +	struct mxl111sf_state *state = d_to_priv(adap_to_d(adap));
> +
> +	mutex_init(&state->msg_lock);
> +}
> +
>  int mxl111sf_ctrl_msg(struct mxl111sf_state *state,
>  		      u8 cmd, u8 *wbuf, int wlen, u8 *rbuf, int rlen)
>  {
> @@ -931,8 +938,6 @@ static int mxl111sf_init(struct dvb_usb_device *d)
>  		  .len = sizeof(eeprom), .buf = eeprom },
>  	};
> 
> -	mutex_init(&state->msg_lock);
> -
>  	ret = get_chip_info(state);
>  	if (mxl_fail(ret))
>  		pr_err("failed to get chip info during probe");
> @@ -963,16 +968,19 @@ static int mxl111sf_init(struct dvb_usb_device *d)
> 
>  static int mxl111sf_frontend_attach_dvbt(struct dvb_usb_adapter *adap)
>  {
> +	mxl111sf_init_msg_mutex(adap);
>  	return mxl111sf_attach_demod(adap, 0);
>  }
> 
>  static int mxl111sf_frontend_attach_atsc(struct dvb_usb_adapter *adap)
>  {
> +	mxl111sf_init_msg_mutex(adap);
>  	return mxl111sf_lgdt3305_frontend_attach(adap, 0);
>  }
> 
>  static int mxl111sf_frontend_attach_mh(struct dvb_usb_adapter *adap)
>  {
> +	mxl111sf_init_msg_mutex(adap);
>  	return mxl111sf_lg2160_frontend_attach(adap, 0);
>  }
> 
> @@ -981,6 +989,7 @@ static int mxl111sf_frontend_attach_atsc_mh(struct
> dvb_usb_adapter *adap)
>  	int ret;
>  	pr_debug("%s\n", __func__);
> 
> +	mxl111sf_init_msg_mutex(adap);
>  	ret = mxl111sf_lgdt3305_frontend_attach(adap, 0);
>  	if (ret < 0)
>  		return ret;
> @@ -1001,6 +1010,7 @@ static int mxl111sf_frontend_attach_mercury(struct
> dvb_usb_adapter *adap)
>  	int ret;
>  	pr_debug("%s\n", __func__);
> 
> +	mxl111sf_init_msg_mutex(adap);
>  	ret = mxl111sf_lgdt3305_frontend_attach(adap, 0);
>  	if (ret < 0)
>  		return ret;
> @@ -1021,6 +1031,7 @@ static int mxl111sf_frontend_attach_mercury_mh(struct
> dvb_usb_adapter *adap)
>  	int ret;
>  	pr_debug("%s\n", __func__);
> 
> +	mxl111sf_init_msg_mutex(adap);
>  	ret = mxl111sf_attach_demod(adap, 0);
>  	if (ret < 0)
>  		return ret;
> 
> 
> 
> With regards,
> Pavel Skripkin

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

[Pavel Skripkin]

On 8/19/21 12:29 PM, Sean Young wrote:
> On Sun, Aug 15, 2021 at 12:06:16PM +0300, Pavel Skripkin wrote:
>> On 8/15/21 11:49 AM, Pavel Skripkin wrote:
>> > 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?
>> > 
>> > 
>> 
>> 
>> Something like this should work. Helper is just to not copy-paste code
>> parts. Build tested against v5.14-rc5
> 
> How about creating a dvb_usb_device_properties probe function and
> initializing the mutex init there?
> 
> 

Sounds reasonable. Will do it in v2, thank you!



With regards,
Pavel Skripkin

[PATCH v2] media: mxl111sf: change mutex_init() location

[Pavel Skripkin]

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@syzkaller.appspotmail.com
Fixes: 8572211842af ("[media] mxl111sf: convert to new DVB USB")
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
---

Changes in v2:
	Addressed same bug in all mxl111sf_* devices by adding ->probe
	call

---
 drivers/media/usb/dvb-usb-v2/mxl111sf.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/media/usb/dvb-usb-v2/mxl111sf.c b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
index 7865fa0a8295..b9714ce994d1 100644
--- a/drivers/media/usb/dvb-usb-v2/mxl111sf.c
+++ b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
@@ -1074,6 +1074,14 @@ static int mxl111sf_get_stream_config_dvbt(struct dvb_frontend *fe,
 	return 0;
 }
 
+static int mxl111sf_probe(struct dvb_usb_device *dev)
+{
+	struct mxl111sf_state *state = d_to_priv(dev);
+
+	mutex_init(&state->msg_lock);
+	return 0;
+}
+
 static struct dvb_usb_device_properties mxl111sf_props_dvbt = {
 	.driver_name = KBUILD_MODNAME,
 	.owner = THIS_MODULE,
@@ -1083,6 +1091,7 @@ static struct dvb_usb_device_properties mxl111sf_props_dvbt = {
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_dvbt,
 	.tuner_attach      = mxl111sf_attach_tuner,
@@ -1124,6 +1133,7 @@ static struct dvb_usb_device_properties mxl111sf_props_atsc = {
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_atsc,
 	.tuner_attach      = mxl111sf_attach_tuner,
@@ -1165,6 +1175,7 @@ static struct dvb_usb_device_properties mxl111sf_props_mh = {
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_mh,
 	.tuner_attach      = mxl111sf_attach_tuner,
@@ -1233,6 +1244,7 @@ static struct dvb_usb_device_properties mxl111sf_props_atsc_mh = {
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_atsc_mh,
 	.tuner_attach      = mxl111sf_attach_tuner,
@@ -1311,6 +1323,7 @@ static struct dvb_usb_device_properties mxl111sf_props_mercury = {
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_mercury,
 	.tuner_attach      = mxl111sf_attach_tuner,
@@ -1381,6 +1394,7 @@ static struct dvb_usb_device_properties mxl111sf_props_mercury_mh = {
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_mercury_mh,
 	.tuner_attach      = mxl111sf_attach_tuner,
-- 
2.32.0

[PATCH v3] media: mxl111sf: change mutex_init() location

[Pavel Skripkin]

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@syzkaller.appspotmail.com
Fixes: 8572211842af ("[media] mxl111sf: convert to new DVB USB")
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
---

Changes in v3:
	I forgot to remove mutex_init() call from ->init()

Changes in v2:
	Addressed same bug in all mxl111sf_* devices by adding ->probe
	call

---
 drivers/media/usb/dvb-usb-v2/mxl111sf.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/dvb-usb-v2/mxl111sf.c b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
index 7865fa0a8295..cd5861a30b6f 100644
--- a/drivers/media/usb/dvb-usb-v2/mxl111sf.c
+++ b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
@@ -931,8 +931,6 @@ static int mxl111sf_init(struct dvb_usb_device *d)
 		  .len = sizeof(eeprom), .buf = eeprom },
 	};
 
-	mutex_init(&state->msg_lock);
-
 	ret = get_chip_info(state);
 	if (mxl_fail(ret))
 		pr_err("failed to get chip info during probe");
@@ -1074,6 +1072,14 @@ static int mxl111sf_get_stream_config_dvbt(struct dvb_frontend *fe,
 	return 0;
 }
 
+static int mxl111sf_probe(struct dvb_usb_device *dev)
+{
+	struct mxl111sf_state *state = d_to_priv(dev);
+
+	mutex_init(&state->msg_lock);
+	return 0;
+}
+
 static struct dvb_usb_device_properties mxl111sf_props_dvbt = {
 	.driver_name = KBUILD_MODNAME,
 	.owner = THIS_MODULE,
@@ -1083,6 +1089,7 @@ static struct dvb_usb_device_properties mxl111sf_props_dvbt = {
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_dvbt,
 	.tuner_attach      = mxl111sf_attach_tuner,
@@ -1124,6 +1131,7 @@ static struct dvb_usb_device_properties mxl111sf_props_atsc = {
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_atsc,
 	.tuner_attach      = mxl111sf_attach_tuner,
@@ -1165,6 +1173,7 @@ static struct dvb_usb_device_properties mxl111sf_props_mh = {
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_mh,
 	.tuner_attach      = mxl111sf_attach_tuner,
@@ -1233,6 +1242,7 @@ static struct dvb_usb_device_properties mxl111sf_props_atsc_mh = {
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_atsc_mh,
 	.tuner_attach      = mxl111sf_attach_tuner,
@@ -1311,6 +1321,7 @@ static struct dvb_usb_device_properties mxl111sf_props_mercury = {
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_mercury,
 	.tuner_attach      = mxl111sf_attach_tuner,
@@ -1381,6 +1392,7 @@ static struct dvb_usb_device_properties mxl111sf_props_mercury_mh = {
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_mercury_mh,
 	.tuner_attach      = mxl111sf_attach_tuner,
-- 
2.32.0

Re: [PATCH v3] media: mxl111sf: change mutex_init() location

[Pavel Skripkin]

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@syzkaller.appspotmail.com
> Fixes: 8572211842af ("[media] mxl111sf: convert to new DVB USB")
> Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>

Hi, Sean!

Did you have a chance to review this patch? Thank you :)


With regards,
Pavel Skripkin

Re: [PATCH v3] media: mxl111sf: change mutex_init() location

[Sean Young]

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@syzkaller.appspotmail.com
> > Fixes: 8572211842af ("[media] mxl111sf: convert to new DVB USB")
> > Signed-off-by: Pavel Skripkin <paskripkin@gmail.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