commit 1b7bde6d659d ("net: fec: implement rx_copybreak to improve rx performance")
introduced a regression for i.MX28. The swap_buffer() function doing
the endian conversion of the received data on i.MX28 may access memory
beyond the actual packet size in the DMA buffer. fec_enet_copybreak()
does not copy those bytes, so that the last bytes of a packet may be
filled with invalid data after swapping.
This will likely lead to checksum errors on received packets.
E.g. when trying to mount an NFS rootfs:
UDP: bad checksum. From 192.168.1.225:111 to 192.168.100.73:44662 ulen 36

Do the byte swapping and copying to the new skb in one go if
necessary.

Signed-off-by: Lothar Wamann <redacted>
---
 drivers/net/ethernet/freescale/fec_main.c |   25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 404fb9d..b92324c 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c

@@ -339,6 +339,18 @@ static void *swap_buffer(void *bufaddr, int len)
 	return bufaddr;
 }

+static void *swap_buffer2(void *dst_buf, void *src_buf, int len)
+{
+	int i;
+	unsigned int *src = src_buf;
+	unsigned int *dst = dst_buf;
+
+	for (i = 0; i < len; i += 4, src++, dst++)
+		swab32s(src);
+
+	return dst_buf;
+}
+