[patch] [media] rc: divide by zero bugs in s_tx_carrier()

[patch] [media] rc: divide by zero bugs in s_tx_carrier()

[Dan Carpenter]

"carrier" comes from a get_user() in ir_lirc_ioctl().  We need to test
that it's not zero before using it as a divisor.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

diff --git a/drivers/media/rc/ene_ir.c b/drivers/media/rc/ene_ir.c
index 647dd95..d05ac15 100644
--- a/drivers/media/rc/ene_ir.c
+++ b/drivers/media/rc/ene_ir.c
@@ -881,10 +881,13 @@ static int ene_set_tx_mask(struct rc_dev *rdev, u32 tx_mask)
 static int ene_set_tx_carrier(struct rc_dev *rdev, u32 carrier)
 {
 	struct ene_device *dev = rdev->priv;
-	u32 period = 2000000 / carrier;
+	u32 period;
 
 	dbg("TX: attempt to set tx carrier to %d kHz", carrier);
+	if (carrier == 0)
+		return -EINVAL;
 
+	period = 2000000 / carrier;
 	if (period && (period > ENE_CIRMOD_PRD_MAX ||
 			period < ENE_CIRMOD_PRD_MIN)) {
 
diff --git a/drivers/media/rc/nuvoton-cir.c b/drivers/media/rc/nuvoton-cir.c
index 699eef3..2ea913a 100644
--- a/drivers/media/rc/nuvoton-cir.c
+++ b/drivers/media/rc/nuvoton-cir.c
@@ -517,6 +517,9 @@ static int nvt_set_tx_carrier(struct rc_dev *dev, u32 carrier)
 	struct nvt_dev *nvt = dev->priv;
 	u16 val;
 
+	if (carrier == 0)
+		return -EINVAL;
+
 	nvt_cir_reg_write(nvt, 1, CIR_CP);
 	val = 3000000 / (carrier) - 1;
 	nvt_cir_reg_write(nvt, val & 0xff, CIR_CC);

Re: [patch] [media] rc: divide by zero bugs in s_tx_carrier()

[Ben Hutchings]

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On Sat, 2012-08-18 at 18:58 +0300, Dan Carpenter wrote:
> "carrier" comes from a get_user() in ir_lirc_ioctl().  We need to test
> that it's not zero before using it as a divisor.

Other RC drivers seem to have the same problem, only more deeply buried.
I think it's better to put this check in ir_lirc_ioctl() instead,
consistent with LIRC_SET_REC_CARRIER.

Ben.

> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> 
> diff --git a/drivers/media/rc/ene_ir.c b/drivers/media/rc/ene_ir.c
> index 647dd95..d05ac15 100644
> --- a/drivers/media/rc/ene_ir.c
> +++ b/drivers/media/rc/ene_ir.c
> @@ -881,10 +881,13 @@ static int ene_set_tx_mask(struct rc_dev *rdev, u32 tx_mask)
>  static int ene_set_tx_carrier(struct rc_dev *rdev, u32 carrier)
>  {
>  	struct ene_device *dev = rdev->priv;
> -	u32 period = 2000000 / carrier;
> +	u32 period;
>  
>  	dbg("TX: attempt to set tx carrier to %d kHz", carrier);
> +	if (carrier == 0)
> +		return -EINVAL;
>  
> +	period = 2000000 / carrier;
>  	if (period && (period > ENE_CIRMOD_PRD_MAX ||
>  			period < ENE_CIRMOD_PRD_MIN)) {
>  
> diff --git a/drivers/media/rc/nuvoton-cir.c b/drivers/media/rc/nuvoton-cir.c
> index 699eef3..2ea913a 100644
> --- a/drivers/media/rc/nuvoton-cir.c
> +++ b/drivers/media/rc/nuvoton-cir.c
> @@ -517,6 +517,9 @@ static int nvt_set_tx_carrier(struct rc_dev *dev, u32 carrier)
>  	struct nvt_dev *nvt = dev->priv;
>  	u16 val;
>  
> +	if (carrier == 0)
> +		return -EINVAL;
> +
>  	nvt_cir_reg_write(nvt, 1, CIR_CP);
>  	val = 3000000 / (carrier) - 1;
>  	nvt_cir_reg_write(nvt, val & 0xff, CIR_CC);
> 

-- 
Ben Hutchings
I say we take off; nuke the site from orbit.  It's the only way to be sure.

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