[U-Boot] [PATCH 2/2] net: designware: clear padding bytes

[Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>]

Short frames are padded to the minimum allowed size of 60 bytes.
However, the designware driver sends old data in these padding bytes.
It is common practice to zero out these padding bytes ro prevent
leaking memory contents to other hosts.

Fix the padding code to zero out the padded bytes at the end.

Tested on socfpga gen5.

Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
---

 drivers/net/designware.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/designware.c b/drivers/net/designware.c
index 688cf9fef2..33463de0f8 100644
--- a/drivers/net/designware.c
+++ b/drivers/net/designware.c
@@ -380,9 +380,11 @@ static int _dw_eth_send(struct dw_eth_dev *priv, void *packet, int length)
 		return -EPERM;
 	}
 
-	length = max(length, ETH_ZLEN);
-
 	memcpy((void *)data_start, packet, length);
+	if (length < ETH_ZLEN) {
+		memset(&((char *)data_start)[length], 0, ETH_ZLEN - length);
+		length = ETH_ZLEN;
+	}
 
 	/* Flush data to be sent */
 	flush_dcache_range(data_start, data_end);
-- 
2.17.1