Commit 804b09be authored by Ido Schimmel's avatar Ido Schimmel Committed by Paolo Abeni
Browse files

vxlan: Add RCU read-side critical sections in the Tx path 



The Tx path does not run from an RCU read-side critical section which
makes the current lockless accesses to FDB entries invalid. As far as I
am aware, this has not been a problem in practice, but traces will be
generated once we transition the FDB lookup to rhashtable_lookup().

Add rcu_read_{lock,unlock}() around the handling of FDB entries in the
Tx path. Remove the RCU read-side critical section from vxlan_xmit_nh()
as now the function is always called from an RCU read-side critical
section.

Reviewed-by: default avatarPetr Machata <petrm@nvidia.com>
Signed-off-by: default avatarIdo Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20250415121143.345227-2-idosch@nvidia.com


Reviewed-by: default avatarNikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 07e32237

drivers/net/vxlan/vxlan_core.c

+8 −6
Original line number Diff line number Diff line
@@ -1916,12 +1916,15 @@ static int arp_reduce(struct net_device *dev, struct sk_buff *skb, __be32 vni) 
			goto out;

		}



		rcu_read_lock();

		f = vxlan_find_mac(vxlan, n->ha, vni);

		if (f && vxlan_addr_any(&(first_remote_rcu(f)->remote_ip))) {

			/* bridge-local neighbor */

			neigh_release(n);

			rcu_read_unlock();

			goto out;

		}

		rcu_read_unlock();



		reply = arp_create(ARPOP_REPLY, ETH_P_ARP, sip, dev, tip, sha,

				n->ha, sha);
@@ -2648,14 +2651,10 @@ static void vxlan_xmit_nh(struct sk_buff *skb, struct net_device *dev, 
	memset(&nh_rdst, 0, sizeof(struct vxlan_rdst));

	hash = skb_get_hash(skb);



	rcu_read_lock();

	nh = rcu_dereference(f->nh);

	if (!nh) {

		rcu_read_unlock();

	if (!nh)

		goto drop;

	}

	do_xmit = vxlan_fdb_nh_path_select(nh, hash, &nh_rdst);

	rcu_read_unlock();



	if (likely(do_xmit))

		vxlan_xmit_one(skb, dev, vni, &nh_rdst, did_rsc);
@@ -2782,6 +2781,7 @@ static netdev_tx_t vxlan_xmit(struct sk_buff *skb, struct net_device *dev) 
	}



	eth = eth_hdr(skb);

	rcu_read_lock();

	f = vxlan_find_mac(vxlan, eth->h_dest, vni);

	did_rsc = false;
@@ -2804,7 +2804,7 @@ static netdev_tx_t vxlan_xmit(struct sk_buff *skb, struct net_device *dev) 
			vxlan_vnifilter_count(vxlan, vni, NULL,

					      VXLAN_VNI_STATS_TX_DROPS, 0);

			kfree_skb_reason(skb, SKB_DROP_REASON_NO_TX_TARGET);

			return NETDEV_TX_OK;

			goto out;

		}

	}
@@ -2829,6 +2829,8 @@ static netdev_tx_t vxlan_xmit(struct sk_buff *skb, struct net_device *dev) 
			kfree_skb_reason(skb, SKB_DROP_REASON_NO_TX_TARGET);

	}



out:

	rcu_read_unlock();

	return NETDEV_TX_OK;

}