Re: [PATCH v2 4/6] USB: hub: fix non-SS hub-descriptor handling

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On Wed, 10 May 2017, Johan Hovold wrote:

> Add missing sanity check on the non-SuperSpeed hub-descriptor length in
> order to avoid parsing and leaking two bytes of uninitialised slab data
> through sysfs removable-attributes (or a compound-device debug
> statement).
> 
> Note that we only make sure that the DeviceRemovable field is always
> present (and specifically ignore the unused PortPwrCtrlMask field) in
> order to continue support any hubs with non-compliant descriptors. As a
> further safeguard, the descriptor buffer is also cleared.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Cc: stable <stable@xxxxxxxxxxxxxxx>     # 2.6.12
> Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
> ---

Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>

>  drivers/usb/core/hub.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 3ff1e9f89f2d..f77a4ebde7d5 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -362,7 +362,8 @@ static void usb_set_lpm_parameters(struct usb_device *udev)
>  }
>  
>  /* USB 2.0 spec Section 11.24.4.5 */
> -static int get_hub_descriptor(struct usb_device *hdev, void *data)
> +static int get_hub_descriptor(struct usb_device *hdev,
> +		struct usb_hub_descriptor *desc)
>  {
>  	int i, ret, size;
>  	unsigned dtype;
> @@ -378,12 +379,16 @@ static int get_hub_descriptor(struct usb_device *hdev, void *data)
>  	for (i = 0; i < 3; i++) {
>  		ret = usb_control_msg(hdev, usb_rcvctrlpipe(hdev, 0),
>  			USB_REQ_GET_DESCRIPTOR, USB_DIR_IN | USB_RT_HUB,
> -			dtype << 8, 0, data, size,
> +			dtype << 8, 0, desc, size,
>  			USB_CTRL_GET_TIMEOUT);
>  		if (hub_is_superspeed(hdev)) {
>  			if (ret == size)
>  				return ret;
> -		} else if (ret >= (USB_DT_HUB_NONVAR_SIZE + 2)) {
> +		} else if (ret >= USB_DT_HUB_NONVAR_SIZE + 2) {
> +			/* Make sure we have the DeviceRemovable field. */
> +			size = USB_DT_HUB_NONVAR_SIZE + desc->bNbrPorts / 8 + 1;
> +			if (ret < size)
> +				return -EMSGSIZE;
>  			return ret;
>  		}
>  	}
> @@ -1317,7 +1322,7 @@ static int hub_configure(struct usb_hub *hub,
>  	}
>  	mutex_init(&hub->status_mutex);
>  
> -	hub->descriptor = kmalloc(sizeof(*hub->descriptor), GFP_KERNEL);
> +	hub->descriptor = kzalloc(sizeof(*hub->descriptor), GFP_KERNEL);
>  	if (!hub->descriptor) {
>  		ret = -ENOMEM;
>  		goto fail;
> 




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