[PATCH net v2 2/2] vxlan: fix reading neigh ha

[Nikolay Aleksandrov <razor@blackwall.org>]

Currently arp/neigh_reduce read neigh ha directly which can lead to
partial reads while the neigh is being updated. Use neigh_ha_snapshot to
take a stable snapshot of the address similar to route_shortcircuit which
already does the right thing.

Fixes: e4f67addf158 ("add DOVE extensions for VXLAN")
Fixes: f564f45c4518 ("vxlan: add ipv6 proxy support")
Signed-off-by: Nikolay Aleksandrov <razor@blackwall.org>
---
v2: - use ETH_ALEN instead of MAX_ADDR_LEN, the bridge devices all use
      ETH_ALEN and vxlan allows arp/nd reduce only when not in raw/gpe
      so it also always uses ETH_ALEN
    - align ha to 2 bytes because ether_addr_copy() expects it (Sashiko)

 drivers/net/vxlan/vxlan_core.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
index 824144bb7774..a94168f7a18e 100644
--- a/drivers/net/vxlan/vxlan_core.c
+++ b/drivers/net/vxlan/vxlan_core.c
@@ -1881,6 +1881,7 @@ static int arp_reduce(struct net_device *dev, struct sk_buff *skb, __be32 vni)
 
 	if (n) {
 		struct vxlan_rdst *rdst = NULL;
+		u8 ha[ETH_ALEN] __aligned(2);
 		struct vxlan_fdb *f;
 		struct sk_buff	*reply;
 
@@ -1889,8 +1890,10 @@ static int arp_reduce(struct net_device *dev, struct sk_buff *skb, __be32 vni)
 			goto out;
 		}
 
+		neigh_ha_snapshot(ha, n, n->dev);
+
 		rcu_read_lock();
-		f = vxlan_find_mac_tx(vxlan, n->ha, vni);
+		f = vxlan_find_mac_tx(vxlan, ha, vni);
 		if (f)
 			rdst = first_remote_rcu(f);
 		if (rdst && vxlan_addr_any(&rdst->remote_ip)) {
@@ -1902,7 +1905,7 @@ static int arp_reduce(struct net_device *dev, struct sk_buff *skb, __be32 vni)
 		rcu_read_unlock();
 
 		reply = arp_create(ARPOP_REPLY, ETH_P_ARP, sip, dev, tip, sha,
-				n->ha, sha);
+				   ha, sha);
 
 		neigh_release(n);
 
@@ -1935,7 +1938,8 @@ static int arp_reduce(struct net_device *dev, struct sk_buff *skb, __be32 vni)
 
 #if IS_ENABLED(CONFIG_IPV6)
 static struct sk_buff *vxlan_na_create(struct sk_buff *request,
-	struct neighbour *n, bool isrouter)
+				       struct neighbour *n, u8 *ha,
+				       bool isrouter)
 {
 	struct net_device *dev = request->dev;
 	struct sk_buff *reply;
@@ -1981,7 +1985,7 @@ static struct sk_buff *vxlan_na_create(struct sk_buff *request,
 
 	/* Ethernet header */
 	ether_addr_copy(eth_hdr(reply)->h_dest, daddr);
-	ether_addr_copy(eth_hdr(reply)->h_source, n->ha);
+	ether_addr_copy(eth_hdr(reply)->h_source, ha);
 	eth_hdr(reply)->h_proto = htons(ETH_P_IPV6);
 	reply->protocol = htons(ETH_P_IPV6);
 
@@ -2010,7 +2014,7 @@ static struct sk_buff *vxlan_na_create(struct sk_buff *request,
 	na->icmph.icmp6_override = 1;
 	na->icmph.icmp6_solicited = 1;
 	na->target = ns->target;
-	ether_addr_copy(&na->opt[2], n->ha);
+	ether_addr_copy(&na->opt[2], ha);
 	na->opt[0] = ND_OPT_TARGET_LL_ADDR;
 	na->opt[1] = na_olen >> 3;
 
@@ -2051,6 +2055,7 @@ static int neigh_reduce(struct net_device *dev, struct sk_buff *skb, __be32 vni)
 
 	if (n) {
 		struct vxlan_rdst *rdst = NULL;
+		u8 ha[ETH_ALEN] __aligned(2);
 		struct vxlan_fdb *f;
 		struct sk_buff *reply;
 
@@ -2059,7 +2064,8 @@ static int neigh_reduce(struct net_device *dev, struct sk_buff *skb, __be32 vni)
 			goto out;
 		}
 
-		f = vxlan_find_mac_tx(vxlan, n->ha, vni);
+		neigh_ha_snapshot(ha, n, n->dev);
+		f = vxlan_find_mac_tx(vxlan, ha, vni);
 		if (f)
 			rdst = first_remote_rcu(f);
 		if (rdst && vxlan_addr_any(&rdst->remote_ip)) {
@@ -2068,7 +2074,7 @@ static int neigh_reduce(struct net_device *dev, struct sk_buff *skb, __be32 vni)
 			goto out;
 		}
 
-		reply = vxlan_na_create(skb, n,
+		reply = vxlan_na_create(skb, n, ha,
 					!!(f ? f->flags & NTF_ROUTER : 0));
 
 		neigh_release(n);
-- 
2.47.3