[patch 2/2] staging: r8188eu: overflow in rtw_p2p_get_go_device_address()

[patch 2/2] staging: r8188eu: overflow in rtw_p2p_get_go_device_address()

[Dan Carpenter]

The go_devadd_str[] array is two characters too small to hold the
address so we corrupt memory.

I've changed the user space API slightly and I don't have a way to test
if this breaks anything.  In the original code we truncated away the
last digit of the address and the NUL terminator so it was already a bit
broken.

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

diff --git a/drivers/staging/rtl8188eu/os_dep/ioctl_linux.c b/drivers/staging/rtl8188eu/os_dep/ioctl_linux.c
index dec992569476..4ad80ae1067f 100644
--- a/drivers/staging/rtl8188eu/os_dep/ioctl_linux.c
+++ b/drivers/staging/rtl8188eu/os_dep/ioctl_linux.c
@@ -3164,9 +3164,7 @@ static int rtw_p2p_get_go_device_address(struct net_device *dev,
 	u8 *p2pie;
 	uint p2pielen = 0, attr_contentlen = 0;
 	u8 attr_content[100] = {0x00};
-
-	u8 go_devadd_str[17 + 10] = {0x00};
-	/*  +10 is for the str "go_devadd =", we have to clear it at wrqu->data.pointer */
+	u8 go_devadd_str[17 + 12] = {};
 
 	/*	Commented by Albert 20121209 */
 	/*	The input data is the GO's interface address which the application wants to know its device address. */
@@ -3223,12 +3221,12 @@ static int rtw_p2p_get_go_device_address(struct net_device *dev,
 	spin_unlock_bh(&pmlmepriv->scanned_queue.lock);
 
 	if (!blnMatch)
-		sprintf(go_devadd_str, "\n\ndev_add = NULL");
+		snprintf(go_devadd_str, sizeof(go_devadd_str), "\n\ndev_add = NULL");
 	else
-		sprintf(go_devadd_str, "\n\ndev_add =%.2X:%.2X:%.2X:%.2X:%.2X:%.2X",
+		snprintf(go_devadd_str, sizeof(go_devadd_str), "\n\ndev_add =%.2X:%.2X:%.2X:%.2X:%.2X:%.2X",
 			attr_content[0], attr_content[1], attr_content[2], attr_content[3], attr_content[4], attr_content[5]);
 
-	if (copy_to_user(wrqu->data.pointer, go_devadd_str, 10 + 17))
+	if (copy_to_user(wrqu->data.pointer, go_devadd_str, sizeof(go_devadd_str)))
 		return -EFAULT;
 	return ret;
 }

Re: [patch 2/2] staging: r8188eu: overflow in rtw_p2p_get_go_device_address()

[Larry Finger]

On 02/03/2014 04:38 PM, Dan Carpenter wrote:
> The go_devadd_str[] array is two characters too small to hold the
> address so we corrupt memory.
>
> I've changed the user space API slightly and I don't have a way to test
> if this breaks anything.  In the original code we truncated away the
> last digit of the address and the NUL terminator so it was already a bit
> broken.
>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Nothing seems to be broken.

Acked-by: Larry Finger <Larry.Finger@lwfinger.net>

Larry

>
> diff --git a/drivers/staging/rtl8188eu/os_dep/ioctl_linux.c b/drivers/staging/rtl8188eu/os_dep/ioctl_linux.c
> index dec992569476..4ad80ae1067f 100644
> --- a/drivers/staging/rtl8188eu/os_dep/ioctl_linux.c
> +++ b/drivers/staging/rtl8188eu/os_dep/ioctl_linux.c
> @@ -3164,9 +3164,7 @@ static int rtw_p2p_get_go_device_address(struct net_device *dev,
>   	u8 *p2pie;
>   	uint p2pielen = 0, attr_contentlen = 0;
>   	u8 attr_content[100] = {0x00};
> -
> -	u8 go_devadd_str[17 + 10] = {0x00};
> -	/*  +10 is for the str "go_devadd =", we have to clear it at wrqu->data.pointer */
> +	u8 go_devadd_str[17 + 12] = {};
>
>   	/*	Commented by Albert 20121209 */
>   	/*	The input data is the GO's interface address which the application wants to know its device address. */
> @@ -3223,12 +3221,12 @@ static int rtw_p2p_get_go_device_address(struct net_device *dev,
>   	spin_unlock_bh(&pmlmepriv->scanned_queue.lock);
>
>   	if (!blnMatch)
> -		sprintf(go_devadd_str, "\n\ndev_add = NULL");
> +		snprintf(go_devadd_str, sizeof(go_devadd_str), "\n\ndev_add = NULL");
>   	else
> -		sprintf(go_devadd_str, "\n\ndev_add =%.2X:%.2X:%.2X:%.2X:%.2X:%.2X",
> +		snprintf(go_devadd_str, sizeof(go_devadd_str), "\n\ndev_add =%.2X:%.2X:%.2X:%.2X:%.2X:%.2X",
>   			attr_content[0], attr_content[1], attr_content[2], attr_content[3], attr_content[4], attr_content[5]);
>
> -	if (copy_to_user(wrqu->data.pointer, go_devadd_str, 10 + 17))
> +	if (copy_to_user(wrqu->data.pointer, go_devadd_str, sizeof(go_devadd_str)))
>   		return -EFAULT;
>   	return ret;
>   }
>

Re: [patch 2/2] staging: r8188eu: overflow in rtw_p2p_get_go_device_address()

[walter harms]

Am 03.02.2014 23:38, schrieb Dan Carpenter:
> The go_devadd_str[] array is two characters too small to hold the
> address so we corrupt memory.
> 
> I've changed the user space API slightly and I don't have a way to test
> if this breaks anything.  In the original code we truncated away the
> last digit of the address and the NUL terminator so it was already a bit
> broken.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> 
> diff --git a/drivers/staging/rtl8188eu/os_dep/ioctl_linux.c b/drivers/staging/rtl8188eu/os_dep/ioctl_linux.c
> index dec992569476..4ad80ae1067f 100644
> --- a/drivers/staging/rtl8188eu/os_dep/ioctl_linux.c
> +++ b/drivers/staging/rtl8188eu/os_dep/ioctl_linux.c
> @@ -3164,9 +3164,7 @@ static int rtw_p2p_get_go_device_address(struct net_device *dev,
>  	u8 *p2pie;
>  	uint p2pielen = 0, attr_contentlen = 0;
>  	u8 attr_content[100] = {0x00};
> -
> -	u8 go_devadd_str[17 + 10] = {0x00};
> -	/*  +10 is for the str "go_devadd =", we have to clear it at wrqu->data.pointer */
> +	u8 go_devadd_str[17 + 12] = {};


you are deleting the explanation for the magic numbers here,
- intentionally  ?

NTL, it would be nice to have a full explanation like
 10= space for  "go_devadd ="
 17= space for attr_content %.2X:%.2X:%.2X:%.2X:%.2X:%.2X
re,
 wh

>  	/*	Commented by Albert 20121209 */
>  	/*	The input data is the GO's interface address which the application wants to know its device address. */
> @@ -3223,12 +3221,12 @@ static int rtw_p2p_get_go_device_address(struct net_device *dev,
>  	spin_unlock_bh(&pmlmepriv->scanned_queue.lock);
>  
>  	if (!blnMatch)
> -		sprintf(go_devadd_str, "\n\ndev_add = NULL");
> +		snprintf(go_devadd_str, sizeof(go_devadd_str), "\n\ndev_add = NULL");
>  	else
> -		sprintf(go_devadd_str, "\n\ndev_add =%.2X:%.2X:%.2X:%.2X:%.2X:%.2X",
> +		snprintf(go_devadd_str, sizeof(go_devadd_str), "\n\ndev_add =%.2X:%.2X:%.2X:%.2X:%.2X:%.2X",
>  			attr_content[0], attr_content[1], attr_content[2], attr_content[3], attr_content[4], attr_content[5]);
>  
> -	if (copy_to_user(wrqu->data.pointer, go_devadd_str, 10 + 17))
> +	if (copy_to_user(wrqu->data.pointer, go_devadd_str, sizeof(go_devadd_str)))
>  		return -EFAULT;
>  	return ret;
>  }
> --
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Re: [patch 2/2] staging: r8188eu: overflow in rtw_p2p_get_go_device_address()

[Dan Carpenter]

On Fri, Feb 07, 2014 at 11:46:26AM +0100, walter harms wrote:
> 
> 
> Am 03.02.2014 23:38, schrieb Dan Carpenter:
> > The go_devadd_str[] array is two characters too small to hold the
> > address so we corrupt memory.
> > 
> > I've changed the user space API slightly and I don't have a way to test
> > if this breaks anything.  In the original code we truncated away the
> > last digit of the address and the NUL terminator so it was already a bit
> > broken.
> > 
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > 
> > diff --git a/drivers/staging/rtl8188eu/os_dep/ioctl_linux.c b/drivers/staging/rtl8188eu/os_dep/ioctl_linux.c
> > index dec992569476..4ad80ae1067f 100644
> > --- a/drivers/staging/rtl8188eu/os_dep/ioctl_linux.c
> > +++ b/drivers/staging/rtl8188eu/os_dep/ioctl_linux.c
> > @@ -3164,9 +3164,7 @@ static int rtw_p2p_get_go_device_address(struct net_device *dev,
> >  	u8 *p2pie;
> >  	uint p2pielen = 0, attr_contentlen = 0;
> >  	u8 attr_content[100] = {0x00};
> > -
> > -	u8 go_devadd_str[17 + 10] = {0x00};
> > -	/*  +10 is for the str "go_devadd =", we have to clear it at wrqu->data.pointer */
> > +	u8 go_devadd_str[17 + 12] = {};
> 
> 
> you are deleting the explanation for the magic numbers here,
> - intentionally  ?
> 

Yes.  The old explanation was misleading because the string is
"\n\ndev_add =" and not "go_devadd =".  The buffer is only used in one
location so the size is obvious and there is no need for a comment.

regards,
dan carpenter