[PATCH] [media] stv090x: do not unlock unheld mutex in stv090x_sleep()

[PATCH] [media] stv090x: do not unlock unheld mutex in stv090x_sleep()

[Alexey Khoroshilov]

goto err and goto err_gateoff before mutex_lock(&state->internal->demod_lock)
lead to unlock of unheld mutex in stv090x_sleep().

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
---
 drivers/media/dvb-frontends/stv090x.c |   22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/drivers/media/dvb-frontends/stv090x.c b/drivers/media/dvb-frontends/stv090x.c
index 13caec0..4f600ac 100644
--- a/drivers/media/dvb-frontends/stv090x.c
+++ b/drivers/media/dvb-frontends/stv090x.c
@@ -3906,12 +3906,12 @@ static int stv090x_sleep(struct dvb_frontend *fe)
 		reg = stv090x_read_reg(state, STV090x_TSTTNR1);
 		STV090x_SETFIELD(reg, ADC1_PON_FIELD, 0);
 		if (stv090x_write_reg(state, STV090x_TSTTNR1, reg) < 0)
-			goto err;
+			goto err_unlock;
 		/* power off DiSEqC 1 */
 		reg = stv090x_read_reg(state, STV090x_TSTTNR2);
 		STV090x_SETFIELD(reg, DISEQC1_PON_FIELD, 0);
 		if (stv090x_write_reg(state, STV090x_TSTTNR2, reg) < 0)
-			goto err;
+			goto err_unlock;
 
 		/* check whether path 2 is already sleeping, that is when
 		   ADC2 is off */
@@ -3930,7 +3930,7 @@ static int stv090x_sleep(struct dvb_frontend *fe)
 		if (full_standby)
 			STV090x_SETFIELD(reg, STOP_CLKFEC_FIELD, 1);
 		if (stv090x_write_reg(state, STV090x_STOPCLK1, reg) < 0)
-			goto err;
+			goto err_unlock;
 		reg = stv090x_read_reg(state, STV090x_STOPCLK2);
 		/* sampling 1 clock */
 		STV090x_SETFIELD(reg, STOP_CLKSAMP1_FIELD, 1);
@@ -3941,7 +3941,7 @@ static int stv090x_sleep(struct dvb_frontend *fe)
 		if (full_standby)
 			STV090x_SETFIELD(reg, STOP_CLKTS_FIELD, 1);
 		if (stv090x_write_reg(state, STV090x_STOPCLK2, reg) < 0)
-			goto err;
+			goto err_unlock;
 		break;
 
 	case STV090x_DEMODULATOR_1:
@@ -3949,12 +3949,12 @@ static int stv090x_sleep(struct dvb_frontend *fe)
 		reg = stv090x_read_reg(state, STV090x_TSTTNR3);
 		STV090x_SETFIELD(reg, ADC2_PON_FIELD, 0);
 		if (stv090x_write_reg(state, STV090x_TSTTNR3, reg) < 0)
-			goto err;
+			goto err_unlock;
 		/* power off DiSEqC 2 */
 		reg = stv090x_read_reg(state, STV090x_TSTTNR4);
 		STV090x_SETFIELD(reg, DISEQC2_PON_FIELD, 0);
 		if (stv090x_write_reg(state, STV090x_TSTTNR4, reg) < 0)
-			goto err;
+			goto err_unlock;
 
 		/* check whether path 1 is already sleeping, that is when
 		   ADC1 is off */
@@ -3973,7 +3973,7 @@ static int stv090x_sleep(struct dvb_frontend *fe)
 		if (full_standby)
 			STV090x_SETFIELD(reg, STOP_CLKFEC_FIELD, 1);
 		if (stv090x_write_reg(state, STV090x_STOPCLK1, reg) < 0)
-			goto err;
+			goto err_unlock;
 		reg = stv090x_read_reg(state, STV090x_STOPCLK2);
 		/* sampling 2 clock */
 		STV090x_SETFIELD(reg, STOP_CLKSAMP2_FIELD, 1);
@@ -3984,7 +3984,7 @@ static int stv090x_sleep(struct dvb_frontend *fe)
 		if (full_standby)
 			STV090x_SETFIELD(reg, STOP_CLKTS_FIELD, 1);
 		if (stv090x_write_reg(state, STV090x_STOPCLK2, reg) < 0)
-			goto err;
+			goto err_unlock;
 		break;
 
 	default:
@@ -3997,7 +3997,7 @@ static int stv090x_sleep(struct dvb_frontend *fe)
 		reg = stv090x_read_reg(state, STV090x_SYNTCTRL);
 		STV090x_SETFIELD(reg, STANDBY_FIELD, 0x01);
 		if (stv090x_write_reg(state, STV090x_SYNTCTRL, reg) < 0)
-			goto err;
+			goto err_unlock;
 	}
 
 	mutex_unlock(&state->internal->demod_lock);
@@ -4005,8 +4005,10 @@ static int stv090x_sleep(struct dvb_frontend *fe)
 
 err_gateoff:
 	stv090x_i2c_gate_ctrl(state, 0);
-err:
+	goto err;
+err_unlock:
 	mutex_unlock(&state->internal->demod_lock);
+err:
 	dprintk(FE_ERROR, 1, "I/O error");
 	return -1;
 }
-- 
1.7.9.5

Re: [PATCH] [media] stv090x: do not unlock unheld mutex in stv090x_sleep()

[Manu Abraham]

Hi,

On Wed, Feb 20, 2013 at 12:28 AM, Alexey Khoroshilov
<khoroshilov@ispras.ru> wrote:
> goto err and goto err_gateoff before mutex_lock(&state->internal->demod_lock)
> lead to unlock of unheld mutex in stv090x_sleep().

Out of curiosity, what happens when you try to unlock an unlocked mutex ?

Regards,
Manu

Re: [PATCH] [media] stv090x: do not unlock unheld mutex in stv090x_sleep()

[Alexey Khoroshilov]

On 02/20/2013 10:58 AM, Manu Abraham wrote:
> Hi,
>
> On Wed, Feb 20, 2013 at 12:28 AM, Alexey Khoroshilov
> <khoroshilov@ispras.ru> wrote:
>> goto err and goto err_gateoff before mutex_lock(&state->internal->demod_lock)
>> lead to unlock of unheld mutex in stv090x_sleep().
> Out of curiosity, what happens when you try to unlock an unlocked mutex ?
>
> Regards,
> Manu
>
Bad things can happen if someone else holds the mutex and it becomes
unexpectedly unlocked.
Also it can result that the next lock() operation leaves the mutex in
unlocked state.
The both cases can lead to data races with unpredictable consequences.

--
Alexey Khoroshilov