[RFC] [media] dvb-core: check ->msg_len for diseqc_send_master_cmd()

[RFC] [media] dvb-core: check ->msg_len for diseqc_send_master_cmd()

[Dan Carpenter]

I'd like to send this patch except that it "breaks"
cx24116_send_diseqc_msg().  The cx24116 driver accepts ->msg_len values
up to 24 but it looks like it's just copying 16 bytes past the end of
the ->msg[] array so it's already broken.

cmd->msg_len is an unsigned char.  The comment next to the struct
declaration says that valid values are are 3-6.  Some of the drivers
check that this is true, but most don't and it could cause memory
corruption.

Some examples of functions which don't check are:
ttusbdecfe_dvbs_diseqc_send_master_cmd()
cx24123_send_diseqc_msg()
ds3000_send_diseqc_msg()
etc.

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

diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
index 57601c0..3d1eee6 100644
--- a/drivers/media/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb-core/dvb_frontend.c
@@ -2265,7 +2265,13 @@ static int dvb_frontend_ioctl_legacy(struct file *file,
 
 	case FE_DISEQC_SEND_MASTER_CMD:
 		if (fe->ops.diseqc_send_master_cmd) {
-			err = fe->ops.diseqc_send_master_cmd(fe, (struct dvb_diseqc_master_cmd*) parg);
+			struct dvb_diseqc_master_cmd *cmd = parg;
+
+			if (cmd->msg_len >= 3 && cmd->msg_len <= 6)
+				err = fe->ops.diseqc_send_master_cmd(fe, cmd);
+			else
+				err = -EINVAL;
+
 			fepriv->state = FESTATE_DISEQC;
 			fepriv->status = 0;
 		}

Re: [RFC] [media] dvb-core: check ->msg_len for diseqc_send_master_cmd()

[Dan Carpenter]

Any feedback on this?

I forgot to CC Steven Toth last time because he would know about the
cx24116 driver.  I've looked at it again and it still looks like
cx24116_send_diseqc_msg() is copying garbage into the
state->dsec_cmd.args[] array.

regards,
dan carpenter

On Tue, Apr 02, 2013 at 10:51:02AM +0300, Dan Carpenter wrote:
> I'd like to send this patch except that it "breaks"
> cx24116_send_diseqc_msg().  The cx24116 driver accepts ->msg_len values
> up to 24 but it looks like it's just copying 16 bytes past the end of
> the ->msg[] array so it's already broken.
> 
> cmd->msg_len is an unsigned char.  The comment next to the struct
> declaration says that valid values are are 3-6.  Some of the drivers
> check that this is true, but most don't and it could cause memory
> corruption.
> 
> Some examples of functions which don't check are:
> ttusbdecfe_dvbs_diseqc_send_master_cmd()
> cx24123_send_diseqc_msg()
> ds3000_send_diseqc_msg()
> etc.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> 
> diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
> index 57601c0..3d1eee6 100644
> --- a/drivers/media/dvb-core/dvb_frontend.c
> +++ b/drivers/media/dvb-core/dvb_frontend.c
> @@ -2265,7 +2265,13 @@ static int dvb_frontend_ioctl_legacy(struct file *file,
>  
>  	case FE_DISEQC_SEND_MASTER_CMD:
>  		if (fe->ops.diseqc_send_master_cmd) {
> -			err = fe->ops.diseqc_send_master_cmd(fe, (struct dvb_diseqc_master_cmd*) parg);
> +			struct dvb_diseqc_master_cmd *cmd = parg;
> +
> +			if (cmd->msg_len >= 3 && cmd->msg_len <= 6)
> +				err = fe->ops.diseqc_send_master_cmd(fe, cmd);
> +			else
> +				err = -EINVAL;
> +
>  			fepriv->state = FESTATE_DISEQC;
>  			fepriv->status = 0;
>  		}

Re: [RFC] [media] dvb-core: check ->msg_len for diseqc_send_master_cmd()

[Antti Palosaari]

On 04/17/2013 03:03 PM, Dan Carpenter wrote:
> Any feedback on this?
>
> I forgot to CC Steven Toth last time because he would know about the
> cx24116 driver.  I've looked at it again and it still looks like
> cx24116_send_diseqc_msg() is copying garbage into the
> state->dsec_cmd.args[] array.

It looks fine. I have thought that same few times earlier too. Thank you.

Reviewed-by: Antti Palosaari <crope@iki.fi>



>
> regards,
> dan carpenter
>
> On Tue, Apr 02, 2013 at 10:51:02AM +0300, Dan Carpenter wrote:
>> I'd like to send this patch except that it "breaks"
>> cx24116_send_diseqc_msg().  The cx24116 driver accepts ->msg_len values
>> up to 24 but it looks like it's just copying 16 bytes past the end of
>> the ->msg[] array so it's already broken.
>>
>> cmd->msg_len is an unsigned char.  The comment next to the struct
>> declaration says that valid values are are 3-6.  Some of the drivers
>> check that this is true, but most don't and it could cause memory
>> corruption.
>>
>> Some examples of functions which don't check are:
>> ttusbdecfe_dvbs_diseqc_send_master_cmd()
>> cx24123_send_diseqc_msg()
>> ds3000_send_diseqc_msg()
>> etc.
>>
>> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>>
>> diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
>> index 57601c0..3d1eee6 100644
>> --- a/drivers/media/dvb-core/dvb_frontend.c
>> +++ b/drivers/media/dvb-core/dvb_frontend.c
>> @@ -2265,7 +2265,13 @@ static int dvb_frontend_ioctl_legacy(struct file *file,
>>
>>   	case FE_DISEQC_SEND_MASTER_CMD:
>>   		if (fe->ops.diseqc_send_master_cmd) {
>> -			err = fe->ops.diseqc_send_master_cmd(fe, (struct dvb_diseqc_master_cmd*) parg);
>> +			struct dvb_diseqc_master_cmd *cmd = parg;
>> +
>> +			if (cmd->msg_len >= 3 && cmd->msg_len <= 6)
>> +				err = fe->ops.diseqc_send_master_cmd(fe, cmd);
>> +			else
>> +				err = -EINVAL;
>> +
>>   			fepriv->state = FESTATE_DISEQC;
>>   			fepriv->status = 0;
>>   		}


-- 
http://palosaari.fi/

Re: [patch] [media] dvb-core: check ->msg_len for diseqc_send_master_cmd()

[Dan Carpenter]

Oops.  I send this to Mauro's old email address.  Sorry about that.

regards,
dan carpenter

On Tue, Apr 01, 2014 at 05:38:07PM +0300, Dan Carpenter wrote:
> I'd like to send this patch except that it "breaks"
> cx24116_send_diseqc_msg().  The cx24116 driver accepts ->msg_len values
> up to 24 but it looks like it's just copying 16 bytes past the end of
> the ->msg[] array so it's already broken.
> 
> cmd->msg_len is an unsigned char.  The comment next to the struct
> declaration says that valid values are are 3-6.  Some of the drivers
> check that this is true, but most don't and it could cause memory
> corruption.
> 
> Some examples of functions which don't check are:
> ttusbdecfe_dvbs_diseqc_send_master_cmd()
> cx24123_send_diseqc_msg()
> ds3000_send_diseqc_msg()
> etc.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> Reviewed-by: Antti Palosaari <crope@iki.fi>
> ---
> This is a static checker fix and I haven't tested it but the security
> implications are quite bad so we should fix this.
> 
> diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
> index 57601c0..3d1eee6 100644
> --- a/drivers/media/dvb-core/dvb_frontend.c
> +++ b/drivers/media/dvb-core/dvb_frontend.c
> @@ -2267,7 +2267,13 @@ static int dvb_frontend_ioctl_legacy(struct file *file,
>  
>  	case FE_DISEQC_SEND_MASTER_CMD:
>  		if (fe->ops.diseqc_send_master_cmd) {
> -			err = fe->ops.diseqc_send_master_cmd(fe, (struct dvb_diseqc_master_cmd*) parg);
> +			struct dvb_diseqc_master_cmd *cmd = parg;
> +
> +			if (cmd->msg_len >= 3 && cmd->msg_len <= 6)
> +				err = fe->ops.diseqc_send_master_cmd(fe, cmd);
> +			else
> +				err = -EINVAL;
> +
>  			fepriv->state = FESTATE_DISEQC;
>  			fepriv->status = 0;
>  		}