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Subject[PATCH 4.14 52/78] net: bcmgenet: use hardware padding of runt frames
From: Doug Berger <>

[ Upstream commit 20d1f2d1b024f6be199a3bedf1578a1d21592bc5 ]

When commit 474ea9cafc45 ("net: bcmgenet: correctly pad short
packets") added the call to skb_padto() it should have been
located before the nr_frags parameter was read since that value
could be changed when padding packets with lengths between 55
and 59 bytes (inclusive).

The use of a stale nr_frags value can cause corruption of the
pad data when tx-scatter-gather is enabled. This corruption of
the pad can cause invalid checksum computation when hardware
offload of tx-checksum is also enabled.

Since the original reason for the padding was corrected by
commit 7dd399130efb ("net: bcmgenet: fix skb_len in
bcmgenet_xmit_single()") we can remove the software padding all
together and make use of hardware padding of short frames as
long as the hardware also always appends the FCS value to the

Fixes: 474ea9cafc45 ("net: bcmgenet: correctly pad short packets")
Signed-off-by: Doug Berger <>
Acked-by: Florian Fainelli <>
Signed-off-by: David S. Miller <>
Signed-off-by: Sasha Levin <>
drivers/net/ethernet/broadcom/genet/bcmgenet.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
index 7d3cbbd88a005..8bfa2523e2533 100644
--- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
@@ -1567,11 +1567,6 @@ static netdev_tx_t bcmgenet_xmit(struct sk_buff *skb, struct net_device *dev)
goto out;

- if (skb_padto(skb, ETH_ZLEN)) {
- ret = NETDEV_TX_OK;
- goto out;
- }
/* Retain how many bytes will be sent on the wire, without TSB inserted
* by transmit checksum offload
@@ -1621,6 +1616,9 @@ static netdev_tx_t bcmgenet_xmit(struct sk_buff *skb, struct net_device *dev)
len_stat = (size << DMA_BUFLENGTH_SHIFT) |
(priv->hw_params->qtag_mask << DMA_TX_QTAG_SHIFT);

+ /* Note: if we ever change from DMA_TX_APPEND_CRC below we
+ * will need to restore software padding of "runt" packets
+ */
if (!i) {
len_stat |= DMA_TX_APPEND_CRC | DMA_SOP;
if (skb->ip_summed == CHECKSUM_PARTIAL)
 \ /
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