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Commit 9ca33a0f authored by Brian Niebuhr's avatar Brian Niebuhr Committed by Greg Kroah-Hartman
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USB: Fix CDC EEM host driver 'sentinel' CRC validation 



This is an alternate solution to the EEM 'sentinel' CRC valiation issue.

CDC EEM allows using a 'sentinel' ethernet frame CRC of 0xdeadbeef in
place of a real CRC.  The 'sentinel' value is transmitted in big-endian
order whereas the normal CRC is little-endian.  This patch handles both
cases appropriately.

Signed-off-by: default avatarBrian Niebuhr <bniebuhr@efjohnson.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 5429c731

drivers/net/usb/cdc_eem.c

+10 −7
Original line number Diff line number Diff line
@@ -300,20 +300,23 @@ static int eem_rx_fixup(struct usbnet *dev, struct sk_buff *skb) 
					return 0;

			}



			crc = get_unaligned_le32(skb2->data

					+ len - ETH_FCS_LEN);

			skb_trim(skb2, len - ETH_FCS_LEN);



			/*

			 * The bmCRC helps to denote when the CRC field in

			 * the Ethernet frame contains a calculated CRC:

			 *	bmCRC = 1	: CRC is calculated

			 *	bmCRC = 0	: CRC = 0xDEADBEEF

			 */

			if (header & BIT(14))

				crc2 = ~crc32_le(~0, skb2->data, skb2->len);

			else

			if (header & BIT(14)) {

				crc = get_unaligned_le32(skb2->data

						+ len - ETH_FCS_LEN);

				crc2 = ~crc32_le(~0, skb2->data, skb2->len

						- ETH_FCS_LEN);

			} else {

				crc = get_unaligned_be32(skb2->data

						+ len - ETH_FCS_LEN);

				crc2 = 0xdeadbeef;

			}

			skb_trim(skb2, len - ETH_FCS_LEN);



			if (is_last)

				return crc == crc2;