ACK: [SRU][Trusty][PATCH 1/1] usbip: fix stub_rx: harden CMD_SUBMIT path to handle malicious input

[Stefan Bader]

On 24.07.2018 13:59, Kleber Sacilotto de Souza wrote:
> From: Shuah Khan <shuahkh at osg.samsung.com>
> 
> commit c6688ef9f29762e65bce325ef4acd6c675806366 upstream.
> 
> Harden CMD_SUBMIT path to handle malicious input that could trigger
> large memory allocations. Add checks to validate transfer_buffer_length
> and number_of_packets to protect against bad input requesting for
> unbounded memory allocations. Validate early in get_pipe() and return
> failure.
> 
> Reported-by: Secunia Research <vuln at secunia.com>
> Signed-off-by: Shuah Khan <shuahkh at osg.samsung.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> 
> CVE-2017-16913
> (backported from commit eebf31529012289ec20fea84e4e6fd188176be13 linux-stable)
> [ klebers: adjusted the file path, the usbip is still under staging on
>   kernel 3.13, and some minor context adjustment. ]
> Signed-off-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>
> ---
>  drivers/staging/usbip/stub_rx.c | 30 +++++++++++++++++++++++++++---
>  1 file changed, 27 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/usbip/stub_rx.c b/drivers/staging/usbip/stub_rx.c
> index db48a789d308..d9262ad46d42 100644
> --- a/drivers/staging/usbip/stub_rx.c
> +++ b/drivers/staging/usbip/stub_rx.c
> @@ -349,11 +349,13 @@ static struct stub_priv *stub_priv_alloc(struct stub_device *sdev,
>  	return priv;
>  }
>  
> -static int get_pipe(struct stub_device *sdev, int epnum, int dir)
> +static int get_pipe(struct stub_device *sdev, struct usbip_header *pdu)
>  {
>  	struct usb_device *udev = sdev->udev;
>  	struct usb_host_endpoint *ep;
>  	struct usb_endpoint_descriptor *epd = NULL;
> +	int epnum = pdu->base.ep;
> +	int dir = pdu->base.direction;
>  
>  	if (dir == USBIP_DIR_IN)
>  		ep = udev->ep_in[epnum & 0x7f];
> @@ -366,6 +368,7 @@ static int get_pipe(struct stub_device *sdev, int epnum, int dir)
>  	}
>  
>  	epd = &ep->desc;
> +
>  	if (usb_endpoint_xfer_control(epd)) {
>  		if (dir == USBIP_DIR_OUT)
>  			return usb_sndctrlpipe(udev, epnum);
> @@ -388,6 +391,27 @@ static int get_pipe(struct stub_device *sdev, int epnum, int dir)
>  	}
>  
>  	if (usb_endpoint_xfer_isoc(epd)) {
> +		/* validate packet size and number of packets */
> +		unsigned int maxp, packets, bytes;
> +
> +#define USB_EP_MAXP_MULT_SHIFT  11
> +#define USB_EP_MAXP_MULT_MASK   (3 << USB_EP_MAXP_MULT_SHIFT)
> +#define USB_EP_MAXP_MULT(m) \
> +	(((m) & USB_EP_MAXP_MULT_MASK) >> USB_EP_MAXP_MULT_SHIFT)
> +
> +		maxp = usb_endpoint_maxp(epd);
> +		maxp *= (USB_EP_MAXP_MULT(
> +				__le16_to_cpu(epd->wMaxPacketSize)) + 1);
> +		bytes = pdu->u.cmd_submit.transfer_buffer_length;
> +		packets = DIV_ROUND_UP(bytes, maxp);
> +
> +		if (pdu->u.cmd_submit.number_of_packets < 0 ||
> +		    pdu->u.cmd_submit.number_of_packets > packets) {
> +			dev_err(&sdev->udev->dev,
> +				"CMD_SUBMIT: isoc invalid num packets %d\n",
> +				pdu->u.cmd_submit.number_of_packets);
> +			return -1;
> +		}
>  		if (dir == USBIP_DIR_OUT)
>  			return usb_sndisocpipe(udev, epnum);
>  		else
> @@ -395,7 +419,7 @@ static int get_pipe(struct stub_device *sdev, int epnum, int dir)
>  	}
>  
>  	/* NOT REACHED */
> -	dev_err(&sdev->interface->dev, "get pipe, epnum %d\n", epnum);
> +	dev_err(&sdev->interface->dev, "CMD_SUBMIT: invalid epnum %d\n", epnum);
>  	return 0;
>  }
>  
> @@ -460,7 +484,7 @@ static void stub_recv_cmd_submit(struct stub_device *sdev,
>  	struct stub_priv *priv;
>  	struct usbip_device *ud = &sdev->ud;
>  	struct usb_device *udev = sdev->udev;
> -	int pipe = get_pipe(sdev, pdu->base.ep, pdu->base.direction);
> +	int pipe = get_pipe(sdev, pdu);
>  
>  	priv = stub_priv_alloc(sdev, pdu);
>  	if (!priv)
> 


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