[PATCH batadv 1/2] batman-adv: ensure u16 aligned mac address arrays on stack

[Sven Eckelmann <sven@narfation.org>]

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