Commit 8d2b1a1e authored by Oliver Neukum's avatar Oliver Neukum Committed by David S. Miller
Browse files

CDC-NCM: avoid overflow in sanity checking 



A broken device may give an extreme offset like 0xFFF0
and a reasonable length for a fragment. In the sanity
check as formulated now, this will create an integer
overflow, defeating the sanity check. Both offset
and offset + len need to be checked in such a manner
that no overflow can occur.
And those quantities should be unsigned.

Signed-off-by: default avatarOliver Neukum <oneukum@suse.com>
Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7e5b6a5c

drivers/net/usb/cdc_ncm.c

+4 −4
Original line number Diff line number Diff line
@@ -1715,10 +1715,10 @@ int cdc_ncm_rx_fixup(struct usbnet *dev, struct sk_buff *skb_in) 
{

	struct sk_buff *skb;

	struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];

	int len;

	unsigned int len;

	int nframes;

	int x;

	int offset;

	unsigned int offset;

	union {

		struct usb_cdc_ncm_ndp16 *ndp16;

		struct usb_cdc_ncm_ndp32 *ndp32;
@@ -1790,8 +1790,8 @@ int cdc_ncm_rx_fixup(struct usbnet *dev, struct sk_buff *skb_in) 
			break;

		}



		/* sanity checking */

		if (((offset + len) > skb_in->len) ||

		/* sanity checking - watch out for integer wrap*/

		if ((offset > skb_in->len) || (len > skb_in->len - offset) ||

				(len > ctx->rx_max) || (len < ETH_HLEN)) {

			netif_dbg(dev, rx_err, dev->net,

				  "invalid frame detected (ignored) offset[%u]=%u, length=%u, skb=%p\n",