linux-kernel - Re: [PATCH] media: cxusb: fix uninitialized local variable

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Date:   Wed, 16 Oct 2019 09:53:34 +0100
From:   Sean Young <sean@...s.org>
To:     Valentin Vidic <vvidic@...entin-vidic.from.hr>
Cc:     Michael Krufky <mkrufky@...uxtv.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzbot+98730b985cad4931a552@...kaller.appspotmail.com
Subject: Re: [PATCH] media: cxusb: fix uninitialized local variable

Hi Valentin,

Thank you for your patch.

On Tue, Oct 15, 2019 at 10:03:15PM +0200, Valentin Vidic wrote:
> Make sure ircode does not contain random values if the call to
> cxusb_ctrl_msg fails for some reason.
> 
> Reported-by: syzbot+98730b985cad4931a552@...kaller.appspotmail.com
> Signed-off-by: Valentin Vidic <vvidic@...entin-vidic.from.hr>
> ---
>  drivers/media/usb/dvb-usb/cxusb.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/usb/dvb-usb/cxusb.c b/drivers/media/usb/dvb-usb/cxusb.c
> index f02fa0a67aa4..afcd88dd96c0 100644
> --- a/drivers/media/usb/dvb-usb/cxusb.c
> +++ b/drivers/media/usb/dvb-usb/cxusb.c
> @@ -519,7 +519,7 @@ static int cxusb_d680_dmb_streaming_ctrl(struct dvb_usb_adapter *adap,
>  
>  static int cxusb_rc_query(struct dvb_usb_device *d)
>  {
> -	u8 ircode[4];
> +	u8 ircode[4] = { 0 };
>  
>  	cxusb_ctrl_msg(d, CMD_GET_IR_CODE, NULL, 0, ircode, 4);

The correct to do here is check the return value of cxusb_ctrl_msg() and
to not proceed if it failed, rather than assume the value of 0.

Also note that:

	https://patchwork.linuxtv.org/patch/59448/

Is already being merged.

Thanks
Sean

>  
> @@ -531,7 +531,7 @@ static int cxusb_rc_query(struct dvb_usb_device *d)
>  
>  static int cxusb_bluebird2_rc_query(struct dvb_usb_device *d)
>  {
> -	u8 ircode[4];
> +	u8 ircode[4] = { 0 };
>  	struct i2c_msg msg = {
>  		.addr = 0x6b,
>  		.flags = I2C_M_RD,
> @@ -550,7 +550,7 @@ static int cxusb_bluebird2_rc_query(struct dvb_usb_device *d)
>  
>  static int cxusb_d680_dmb_rc_query(struct dvb_usb_device *d)
>  {
> -	u8 ircode[2];
> +	u8 ircode[2] = { 0 };
>  
>  	if (cxusb_ctrl_msg(d, 0x10, NULL, 0, ircode, 2) < 0)
>  		return 0;
> @@ -989,7 +989,7 @@ static int cxusb_dee1601_frontend_attach(struct dvb_usb_adapter *adap)
>  
>  static int cxusb_dualdig4_frontend_attach(struct dvb_usb_adapter *adap)
>  {
> -	u8 ircode[4];
> +	u8 ircode[4] = { 0 };
>  	int i;
>  	struct i2c_msg msg = {
>  		.addr = 0x6b,
> -- 
> 2.20.1