* [PATCH batadv 1/2] batman-adv: ensure u16 aligned mac address arrays on stack
2026-08-22 13:14 [PATCH batadv 0/2] batman-adv: enforce u16 MAC address alignment Sven Eckelmann
@ 2026-08-22 13:14 ` Sven Eckelmann
2026-08-22 13:14 ` [PATCH batadv 2/2] batman-adv: ensure u16 aligned mac address in structs Sven Eckelmann
1 sibling, 0 replies; 3+ messages in thread
From: Sven Eckelmann @ 2026-08-22 13:14 UTC (permalink / raw)
To: b.a.t.m.a.n; +Cc: Sven Eckelmann, Sashiko
An u8 array on the stack has a natural alignment of only 1 byte. An
u8[ETH_ALEN] array on the stack must therefore be assumed to only be 1 byte
aligned. But many etherdevices.h functions are requiring a 2 byte (u16)
alignment.
Annote all u8[ETH_ALEN] arrays on the stack as __aligned(2) to make sure
that the compiler takes care of aligning it correctly.
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20260821094813.201800-1-sw%40simonwunderlich.de?part=5
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
net/batman-adv/bridge_loop_avoidance.c | 6 ++++--
net/batman-adv/distributed-arp-table.c | 8 ++++----
net/batman-adv/mesh-interface.c | 12 ++++++++----
net/batman-adv/multicast.c | 6 +++---
4 files changed, 19 insertions(+), 13 deletions(-)
diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c
index f635da4b..ad6ab4a5 100644
--- a/net/batman-adv/bridge_loop_avoidance.c
+++ b/net/batman-adv/bridge_loop_avoidance.c
@@ -663,7 +663,7 @@ static void batadv_bla_send_request(struct batadv_bla_backbone_gw *backbone_gw)
static void batadv_bla_send_announce(struct batadv_priv *bat_priv,
struct batadv_bla_backbone_gw *backbone_gw)
{
- u8 mac[ETH_ALEN];
+ u8 mac[ETH_ALEN] __aligned(2);
__be16 crc;
memcpy(mac, batadv_announce_mac, 4);
@@ -1582,7 +1582,9 @@ static struct lock_class_key batadv_backbone_hash_lock_class_key;
*/
int batadv_bla_init(struct batadv_priv *bat_priv)
{
- u8 claim_dest[ETH_ALEN] = {0xff, 0x43, 0x05, 0x00, 0x00, 0x00};
+ static const u8 claim_dest[ETH_ALEN] __aligned(2) = {
+ 0xff, 0x43, 0x05, 0x00, 0x00, 0x00
+ };
struct batadv_hard_iface *primary_if;
unsigned long entrytime;
u16 crc;
diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c
index 011cfdc4..ae0e45a2 100644
--- a/net/batman-adv/distributed-arp-table.c
+++ b/net/batman-adv/distributed-arp-table.c
@@ -940,7 +940,7 @@ batadv_dat_cache_dump_entry(struct sk_buff *msg, u32 portid,
struct netlink_callback *cb,
struct batadv_dat_entry *dat_entry)
{
- u8 mac[ETH_ALEN];
+ u8 mac[ETH_ALEN] __aligned(2);
u64 u64_mac;
int msecs;
void *hdr;
@@ -1236,10 +1236,10 @@ bool batadv_dat_snoop_outgoing_arp_request(struct batadv_priv *bat_priv,
{
struct net_device *mesh_iface = bat_priv->mesh_iface;
struct batadv_dat_entry *dat_entry = NULL;
+ u8 mac[ETH_ALEN] __aligned(2);
struct sk_buff *skb_new;
unsigned short vid;
bool ret = false;
- u8 mac[ETH_ALEN];
int hdr_size = 0;
__be32 ip_dst;
__be32 ip_src;
@@ -1344,10 +1344,10 @@ bool batadv_dat_snoop_incoming_arp_request(struct batadv_priv *bat_priv,
struct sk_buff *skb, int hdr_size)
{
struct batadv_dat_entry *dat_entry = NULL;
+ u8 mac[ETH_ALEN] __aligned(2);
struct sk_buff *skb_new;
unsigned short vid;
bool ret = false;
- u8 mac[ETH_ALEN];
__be32 ip_src;
__be32 ip_dst;
u64 u64_mac;
@@ -1474,9 +1474,9 @@ bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv,
struct sk_buff *skb, int hdr_size)
{
struct batadv_dat_entry *dat_entry = NULL;
+ u8 mac[ETH_ALEN] __aligned(2);
bool dropped = false;
unsigned short vid;
- u8 mac[ETH_ALEN];
__be32 ip_src;
__be32 ip_dst;
u64 u64_mac;
diff --git a/net/batman-adv/mesh-interface.c b/net/batman-adv/mesh-interface.c
index 53bb9836..3c95d9ce 100644
--- a/net/batman-adv/mesh-interface.c
+++ b/net/batman-adv/mesh-interface.c
@@ -141,9 +141,9 @@ static struct net_device_stats *batadv_interface_stats(struct net_device *dev)
static int batadv_interface_set_mac_addr(struct net_device *dev, void *p)
{
struct batadv_priv *bat_priv = netdev_priv(dev);
+ u8 old_addr[ETH_ALEN] __aligned(2);
struct batadv_meshif_vlan *vlan;
struct sockaddr *addr = p;
- u8 old_addr[ETH_ALEN];
if (!is_valid_ether_addr(addr->sa_data))
return -EADDRNOTAVAIL;
@@ -213,13 +213,18 @@ static void batadv_interface_set_rx_mode(struct net_device *dev)
static netdev_tx_t batadv_interface_tx(struct sk_buff *skb,
struct net_device *mesh_iface)
{
- static const u8 ectp_addr[ETH_ALEN] = {0xCF, 0x00, 0x00, 0x00, 0x00, 0x00};
- static const u8 stp_addr[ETH_ALEN] = {0x01, 0x80, 0xC2, 0x00, 0x00, 0x00};
struct batadv_priv *bat_priv = netdev_priv(mesh_iface);
enum batadv_dhcp_recipient dhcp_rcp = BATADV_DHCP_NO;
enum batadv_forw_mode forw_mode = BATADV_FORW_BCAST;
+ static const u8 ectp_addr[ETH_ALEN] __aligned(2) = {
+ 0xCF, 0x00, 0x00, 0x00, 0x00, 0x00
+ };
+ static const u8 stp_addr[ETH_ALEN] __aligned(2) = {
+ 0x01, 0x80, 0xC2, 0x00, 0x00, 0x00
+ };
struct batadv_hard_iface *primary_if = NULL;
struct batadv_bcast_packet *bcast_packet;
+ u8 chaddr[ETH_ALEN] __aligned(2);
int network_offset = ETH_HLEN;
unsigned int header_len = 0;
unsigned long brd_delay = 0;
@@ -229,7 +234,6 @@ static netdev_tx_t batadv_interface_tx(struct sk_buff *skb,
struct ethhdr *ethhdr;
bool do_bcast = false;
u8 *dst_hint = NULL;
- u8 chaddr[ETH_ALEN];
unsigned short vid;
bool client_added;
__be16 proto;
diff --git a/net/batman-adv/multicast.c b/net/batman-adv/multicast.c
index 155592ab..4a92f672 100644
--- a/net/batman-adv/multicast.c
+++ b/net/batman-adv/multicast.c
@@ -374,9 +374,9 @@ batadv_mcast_mla_meshif_get_ipv4(struct net_device *dev,
struct hlist_head *mcast_list,
struct batadv_mcast_mla_flags *flags)
{
+ u8 mcast_addr[ETH_ALEN] __aligned(2);
struct batadv_hw_addr *new;
struct in_device *in_dev;
- u8 mcast_addr[ETH_ALEN];
struct ip_mc_list *pmc;
int ret = 0;
@@ -441,9 +441,9 @@ batadv_mcast_mla_meshif_get_ipv6(struct net_device *dev,
struct hlist_head *mcast_list,
struct batadv_mcast_mla_flags *flags)
{
+ u8 mcast_addr[ETH_ALEN] __aligned(2);
struct batadv_hw_addr *new;
struct inet6_dev *in6_dev;
- u8 mcast_addr[ETH_ALEN];
struct ifmcaddr6 *pmc6;
int ret = 0;
@@ -593,10 +593,10 @@ static int batadv_mcast_mla_bridge_get(struct net_device *dev,
struct batadv_mcast_mla_flags *flags)
{
struct list_head bridge_mcast_list = LIST_HEAD_INIT(bridge_mcast_list);
+ u8 mcast_addr[ETH_ALEN] __aligned(2);
u8 tvlv_flags = flags->tvlv_flags;
struct br_ip_list *br_ip_entry;
struct batadv_hw_addr *new;
- u8 mcast_addr[ETH_ALEN];
struct br_ip_list *tmp;
int ret;
--
2.47.3
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH batadv 2/2] batman-adv: ensure u16 aligned mac address in structs
2026-08-22 13:14 [PATCH batadv 0/2] batman-adv: enforce u16 MAC address alignment Sven Eckelmann
2026-08-22 13:14 ` [PATCH batadv 1/2] batman-adv: ensure u16 aligned mac address arrays on stack Sven Eckelmann
@ 2026-08-22 13:14 ` Sven Eckelmann
1 sibling, 0 replies; 3+ messages in thread
From: Sven Eckelmann @ 2026-08-22 13:14 UTC (permalink / raw)
To: b.a.t.m.a.n; +Cc: Sven Eckelmann
An u8 array in structures have a natural alignment of only 1 byte. An
u8[ETH_ALEN] array must therefore be assumed to only be 1 byte aligned. But
many etherdevices.h functions are requiring a 2 byte (u16) alignment.
All these addresses were either on the start of a struct or after a struct
member which required at least an alignment of 2 byte. Still, annote all
u8[ETH_ALEN] arrays on the stack as __aligned(2) to make sure that this
assumption isn't broken by other modifications inside the structs.
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
net/batman-adv/types.h | 26 +++++++++++++-------------
1 file changed, 13 insertions(+), 13 deletions(-)
diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 9bdc5a3e..c4bfd4cd 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -410,7 +410,7 @@ struct batadv_orig_bat_iv {
*/
struct batadv_orig_node {
/** @orig: originator ethernet address */
- u8 orig[ETH_ALEN];
+ u8 orig[ETH_ALEN] __aligned(2);
/** @ifinfo_list: list for routers per outgoing interface */
struct hlist_head ifinfo_list;
@@ -634,12 +634,12 @@ struct batadv_hardif_neigh_node {
struct hlist_node list;
/** @addr: the MAC address of the neighboring interface */
- u8 addr[ETH_ALEN];
+ u8 addr[ETH_ALEN] __aligned(2);
/**
* @orig: the address of the originator this neighbor node belongs to
*/
- u8 orig[ETH_ALEN];
+ u8 orig[ETH_ALEN] __aligned(2);
/** @if_incoming: pointer to incoming hard-interface */
struct batadv_hard_iface *if_incoming;
@@ -677,7 +677,7 @@ struct batadv_neigh_node {
#endif
/** @addr: the MAC address of the neighboring interface */
- u8 addr[ETH_ALEN];
+ u8 addr[ETH_ALEN] __aligned(2);
/** @ifinfo_list: list for routing metrics per outgoing interface */
struct hlist_head ifinfo_list;
@@ -777,7 +777,7 @@ struct batadv_neigh_ifinfo {
*/
struct batadv_bcast_duplist_entry {
/** @orig: mac address of orig node originating the broadcast */
- u8 orig[ETH_ALEN];
+ u8 orig[ETH_ALEN] __aligned(2);
/** @crc: crc32 checksum of broadcast payload */
u32 crc;
@@ -1085,7 +1085,7 @@ struct batadv_priv_bla {
struct batadv_hashtable *backbone_hash;
/** @loopdetect_addr: MAC address used for own loopdetection frames */
- u8 loopdetect_addr[ETH_ALEN];
+ u8 loopdetect_addr[ETH_ALEN] __aligned(2);
/**
* @loopdetect_lasttime: time when the loopdetection frames were sent
@@ -1352,7 +1352,7 @@ struct batadv_tp_vars_common {
struct batadv_priv *bat_priv;
/** @other_end: mac address of remote */
- u8 other_end[ETH_ALEN];
+ u8 other_end[ETH_ALEN] __aligned(2);
/** @session: TP session identifier */
u8 session[2];
@@ -1765,7 +1765,7 @@ struct batadv_bla_backbone_gw {
* @orig: originator address of backbone node (mac address of primary
* iface)
*/
- u8 orig[ETH_ALEN];
+ u8 orig[ETH_ALEN] __aligned(2);
/** @vid: vlan id this gateway was detected on */
unsigned short vid;
@@ -1810,7 +1810,7 @@ struct batadv_bla_backbone_gw {
*/
struct batadv_bla_claim {
/** @addr: mac address of claimed non-mesh client */
- u8 addr[ETH_ALEN];
+ u8 addr[ETH_ALEN] __aligned(2);
/** @vid: vlan id this client was detected on */
unsigned short vid;
@@ -1840,7 +1840,7 @@ struct batadv_bla_claim {
*/
struct batadv_tt_common_entry {
/** @addr: mac address of non-mesh client */
- u8 addr[ETH_ALEN];
+ u8 addr[ETH_ALEN] __aligned(2);
/** @vid: VLAN identifier */
unsigned short vid;
@@ -1942,7 +1942,7 @@ struct batadv_tt_req_node {
/**
* @addr: mac address of the originator this request was sent to
*/
- u8 addr[ETH_ALEN];
+ u8 addr[ETH_ALEN] __aligned(2);
/** @issued_at: timestamp used for purging stale tt requests */
unsigned long issued_at;
@@ -1959,7 +1959,7 @@ struct batadv_tt_req_node {
*/
struct batadv_tt_roam_node {
/** @addr: mac address of the client in the roaming phase */
- u8 addr[ETH_ALEN];
+ u8 addr[ETH_ALEN] __aligned(2);
/** @vid: VLAN identifier */
u16 vid;
@@ -2204,7 +2204,7 @@ struct batadv_hw_addr {
struct hlist_node list;
/** @addr: the MAC address of this list entry */
- unsigned char addr[ETH_ALEN];
+ unsigned char addr[ETH_ALEN] __aligned(2);
};
/**
--
2.47.3
^ permalink raw reply related [flat|nested] 3+ messages in thread