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: Brian Niebuhr <bniebuhr@efjohnson.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 10 insertions, 7 deletions

diff --git a/drivers/net/usb/cdc_eem.c b/drivers/net/usb/cdc_eem.c
index 45cebfb302cf..23300656c266 100644
--- a/drivers/net/usb/cdc_eem.c
+++ b/drivers/net/usb/cdc_eem.c
@@ -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;