[PATCH v2 net] bonding: use skb_cow_head() in bond_do_alb_xmit() and rlb_arp_xmit()
From: Eric Dumazet <edumazet@google.com>
Date: 2026-09-03 14:39:45
Subsystem:
bonding driver, networking drivers, the rest · Maintainers:
Jay Vosburgh, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
In bond_do_alb_xmit() and rlb_arp_xmit(), make sure to unclone
skb head via skb_cow_head() before modifying the source MAC address
(Ethernet header and ARP payload) to avoid silent corruption if
the skb is shared or cloned. Avoid caching the header pointers
across skb_cow_head().
In rlb_arp_xmit(), only modify arp->mac_src if it differs from
tx_slave->dev->dev_addr to avoid an unnecessary copy and head
reallocation.
Also, we should not assume mac header is set in output path.
Use skb_eth_hdr() instead of eth_hdr() to fix the issue,
and remove now redundant skb_reset_mac_header() calls.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Hangbin Liu <redacted>
Cc: Jay Vosburgh <jv@jvosburgh.net>
---
v2: Use ether_addr_equal_64bits() per Sashiko AI agent feedback
v1: https://lore.kernel.org/netdev/20260902125809.2910366-1-edumazet@google.com/ (local)
drivers/net/bonding/bond_alb.c | 19 ++++++++++++-------
1 file changed, 12 insertions(+), 7 deletions(-)
diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
index 654f051d0023929a48536c378996e0ef39b75d88..43ac8e28e41828d30fb66f6f562bee5c1af630a7 100644
--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c@@ -678,9 +678,15 @@ static struct slave *rlb_arp_xmit(struct sk_buff *skb, struct bonding *bond) if (arp->op_code == htons(ARPOP_REPLY)) { /* the arp must be sent on the selected rx channel */ tx_slave = rlb_choose_channel(skb, bond, arp); - if (tx_slave) + if (tx_slave && + !ether_addr_equal_64bits(arp->mac_src, + tx_slave->dev->dev_addr)) { + if (unlikely(skb_cow_head(skb, 0))) + return NULL; + arp = (struct arp_pkt *)skb_network_header(skb); bond_hw_addr_copy(arp->mac_src, tx_slave->dev->dev_addr, tx_slave->dev->addr_len); + } netdev_dbg(bond->dev, "(slave %s): Server sent ARP Reply packet\n", tx_slave ? tx_slave->dev->name : "NULL"); } else if (arp->op_code == htons(ARPOP_REQUEST)) {
@@ -1340,7 +1346,6 @@ static netdev_tx_t bond_do_alb_xmit(struct sk_buff *skb, struct bonding *bond, struct slave *tx_slave) { struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond)); - struct ethhdr *eth_data = eth_hdr(skb); if (!tx_slave) { /* unbalanced or unassigned, send through primary */
@@ -1351,7 +1356,9 @@ static netdev_tx_t bond_do_alb_xmit(struct sk_buff *skb, struct bonding *bond, if (tx_slave && bond_slave_can_tx(tx_slave)) { if (tx_slave != rcu_access_pointer(bond->curr_active_slave)) { - ether_addr_copy(eth_data->h_source, + if (unlikely(skb_cow_head(skb, 0))) + return bond_tx_drop(bond->dev, skb); + ether_addr_copy(skb_eth_hdr(skb)->h_source, tx_slave->dev->dev_addr); }
@@ -1375,8 +1382,7 @@ struct slave *bond_xmit_tlb_slave_get(struct bonding *bond, struct ethhdr *eth_data; u32 hash_index; - skb_reset_mac_header(skb); - eth_data = eth_hdr(skb); + eth_data = skb_eth_hdr(skb); /* Do not TX balance any multicast or broadcast */ if (!is_multicast_ether_addr(eth_data->h_dest)) {
@@ -1428,8 +1434,7 @@ struct slave *bond_xmit_alb_slave_get(struct bonding *bond, u32 hash_index = 0; int hash_size = 0; - skb_reset_mac_header(skb); - eth_data = eth_hdr(skb); + eth_data = skb_eth_hdr(skb); switch (ntohs(skb->protocol)) { case ETH_P_IP: {
--
2.55.0.970.g62bdec98f9-goog