KVM: SEV: Do cache maintenance on the source VM during intra-host migrationgrafted

Manually perform cache maintenance on the source VM during intra-host
migration to ensure no stale data is left in CPU caches after the VM is
destroyed.  Because the source VM is "converted" to a non-SEV VM, KVM's
memory reclaim flows won't trigger cache maintenance, e.g. when all guest
memory is reclaimed in response to detaching from the mmu_notifier.

Note, relying on the destination VM to do cache maintenance isn't an option
as KVM doesn't require identical guest memory configurations, i.e. the
source VM may have access to memory that the destination VM does not.
Enforcing equivalent memory configurations is infeasible, as it would
require a *deep* comparison of memslots, e.g. to verify that not only are
the memslot identical, but what the memslots point at is also identical.

Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
Cc: stable@vger.kernel.org
Reported-by: Stefan Teodorescu <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260923163721.1584779-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 436 insertions, 0 deletions

diff --git a/drivers/net/wireguard/socket.c b/drivers/net/wireguard/socket.c
new file mode 100644
index 000000000..0028ef17d
--- /dev/null
+++ b/drivers/net/wireguard/socket.c
@@ -0,0 +1,436 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#include "device.h"
+#include "peer.h"
+#include "socket.h"
+#include "queueing.h"
+#include "messages.h"
+
+#include <linux/ctype.h>
+#include <linux/net.h>
+#include <linux/if_vlan.h>
+#include <linux/if_ether.h>
+#include <linux/inetdevice.h>
+#include <net/udp_tunnel.h>
+#include <net/ipv6.h>
+
+static int send4(struct wg_device *wg, struct sk_buff *skb,
+		 struct endpoint *endpoint, u8 ds, struct dst_cache *cache)
+{
+	struct flowi4 fl = {
+		.saddr = endpoint->src4.s_addr,
+		.daddr = endpoint->addr4.sin_addr.s_addr,
+		.fl4_dport = endpoint->addr4.sin_port,
+		.flowi4_mark = wg->fwmark,
+		.flowi4_proto = IPPROTO_UDP
+	};
+	struct rtable *rt = NULL;
+	struct sock *sock;
+	int ret = 0;
+
+	skb_mark_not_on_list(skb);
+	skb->dev = wg->dev;
+	skb->mark = wg->fwmark;
+
+	rcu_read_lock_bh();
+	sock = rcu_dereference_bh(wg->sock4);
+
+	if (unlikely(!sock)) {
+		ret = -ENONET;
+		goto err;
+	}
+
+	fl.fl4_sport = inet_sk(sock)->inet_sport;
+
+	if (cache)
+		rt = dst_cache_get_ip4(cache, &fl.saddr);
+
+	if (!rt) {
+		security_sk_classify_flow(sock, flowi4_to_flowi_common(&fl));
+		if (unlikely(!inet_confirm_addr(sock_net(sock), NULL, 0,
+						fl.saddr, RT_SCOPE_HOST))) {
+			endpoint->src4.s_addr = 0;
+			endpoint->src_if4 = 0;
+			fl.saddr = 0;
+			if (cache)
+				dst_cache_reset(cache);
+		}
+		rt = ip_route_output_flow(sock_net(sock), &fl, sock);
+		if (unlikely(endpoint->src_if4 && ((IS_ERR(rt) &&
+			     PTR_ERR(rt) == -EINVAL) || (!IS_ERR(rt) &&
+			     rt->dst.dev->ifindex != endpoint->src_if4)))) {
+			endpoint->src4.s_addr = 0;
+			endpoint->src_if4 = 0;
+			fl.saddr = 0;
+			if (cache)
+				dst_cache_reset(cache);
+			if (!IS_ERR(rt))
+				ip_rt_put(rt);
+			rt = ip_route_output_flow(sock_net(sock), &fl, sock);
+		}
+		if (IS_ERR(rt)) {
+			ret = PTR_ERR(rt);
+			net_dbg_ratelimited("%s: No route to %pISpfsc, error %d\n",
+					    wg->dev->name, &endpoint->addr, ret);
+			goto err;
+		}
+		if (cache)
+			dst_cache_set_ip4(cache, &rt->dst, fl.saddr);
+	}
+
+	skb->ignore_df = 1;
+	udp_tunnel_xmit_skb(rt, sock, skb, fl.saddr, fl.daddr, ds,
+			    ip4_dst_hoplimit(&rt->dst), 0, fl.fl4_sport,
+			    fl.fl4_dport, false, false, 0);
+	goto out;
+
+err:
+	kfree_skb(skb);
+out:
+	rcu_read_unlock_bh();
+	return ret;
+}
+
+static int send6(struct wg_device *wg, struct sk_buff *skb,
+		 struct endpoint *endpoint, u8 ds, struct dst_cache *cache)
+{
+#if IS_ENABLED(CONFIG_IPV6)
+	struct flowi6 fl = {
+		.saddr = endpoint->src6,
+		.daddr = endpoint->addr6.sin6_addr,
+		.fl6_dport = endpoint->addr6.sin6_port,
+		.flowi6_mark = wg->fwmark,
+		.flowi6_oif = endpoint->addr6.sin6_scope_id,
+		.flowi6_proto = IPPROTO_UDP
+		/* TODO: addr->sin6_flowinfo */
+	};
+	struct dst_entry *dst = NULL;
+	struct sock *sock;
+	int ret = 0;
+
+	skb_mark_not_on_list(skb);
+	skb->dev = wg->dev;
+	skb->mark = wg->fwmark;
+
+	rcu_read_lock_bh();
+	sock = rcu_dereference_bh(wg->sock6);
+
+	if (unlikely(!sock)) {
+		ret = -ENONET;
+		goto err;
+	}
+
+	fl.fl6_sport = inet_sk(sock)->inet_sport;
+
+	if (cache)
+		dst = dst_cache_get_ip6(cache, &fl.saddr);
+
+	if (!dst) {
+		security_sk_classify_flow(sock, flowi6_to_flowi_common(&fl));
+		if (unlikely(!ipv6_addr_any(&fl.saddr) &&
+			     !ipv6_chk_addr(sock_net(sock), &fl.saddr, NULL, 0))) {
+			endpoint->src6 = fl.saddr = in6addr_any;
+			if (cache)
+				dst_cache_reset(cache);
+		}
+		dst = ip6_dst_lookup_flow(sock_net(sock), sock, &fl, NULL);
+		if (IS_ERR(dst)) {
+			ret = PTR_ERR(dst);
+			net_dbg_ratelimited("%s: No route to %pISpfsc, error %d\n",
+					    wg->dev->name, &endpoint->addr, ret);
+			goto err;
+		}
+		if (cache)
+			dst_cache_set_ip6(cache, dst, &fl.saddr);
+	}
+
+	skb->ignore_df = 1;
+	udp_tunnel6_xmit_skb(dst, sock, skb, skb->dev, &fl.saddr, &fl.daddr, ds,
+			     ip6_dst_hoplimit(dst), 0, fl.fl6_sport,
+			     fl.fl6_dport, false, 0);
+	goto out;
+
+err:
+	kfree_skb(skb);
+out:
+	rcu_read_unlock_bh();
+	return ret;
+#else
+	kfree_skb(skb);
+	return -EAFNOSUPPORT;
+#endif
+}
+
+int wg_socket_send_skb_to_peer(struct wg_peer *peer, struct sk_buff *skb, u8 ds)
+{
+	size_t skb_len = skb->len;
+	int ret = -EAFNOSUPPORT;
+
+	read_lock_bh(&peer->endpoint_lock);
+	if (peer->endpoint.addr.sa_family == AF_INET)
+		ret = send4(peer->device, skb, &peer->endpoint, ds,
+			    &peer->endpoint_cache);
+	else if (peer->endpoint.addr.sa_family == AF_INET6)
+		ret = send6(peer->device, skb, &peer->endpoint, ds,
+			    &peer->endpoint_cache);
+	else
+		dev_kfree_skb(skb);
+	if (likely(!ret))
+		peer->tx_bytes += skb_len;
+	read_unlock_bh(&peer->endpoint_lock);
+
+	return ret;
+}
+
+int wg_socket_send_buffer_to_peer(struct wg_peer *peer, void *buffer,
+				  size_t len, u8 ds)
+{
+	struct sk_buff *skb = alloc_skb(len + SKB_HEADER_LEN, GFP_ATOMIC);
+
+	if (unlikely(!skb))
+		return -ENOMEM;
+
+	skb_reserve(skb, SKB_HEADER_LEN);
+	skb_set_inner_network_header(skb, 0);
+	skb_put_data(skb, buffer, len);
+	return wg_socket_send_skb_to_peer(peer, skb, ds);
+}
+
+int wg_socket_send_buffer_as_reply_to_skb(struct wg_device *wg,
+					  struct sk_buff *in_skb, void *buffer,
+					  size_t len)
+{
+	int ret = 0;
+	struct sk_buff *skb;
+	struct endpoint endpoint;
+
+	if (unlikely(!in_skb))
+		return -EINVAL;
+	ret = wg_socket_endpoint_from_skb(&endpoint, in_skb);
+	if (unlikely(ret < 0))
+		return ret;
+
+	skb = alloc_skb(len + SKB_HEADER_LEN, GFP_ATOMIC);
+	if (unlikely(!skb))
+		return -ENOMEM;
+	skb_reserve(skb, SKB_HEADER_LEN);
+	skb_set_inner_network_header(skb, 0);
+	skb_put_data(skb, buffer, len);
+
+	if (endpoint.addr.sa_family == AF_INET)
+		ret = send4(wg, skb, &endpoint, 0, NULL);
+	else if (endpoint.addr.sa_family == AF_INET6)
+		ret = send6(wg, skb, &endpoint, 0, NULL);
+	/* No other possibilities if the endpoint is valid, which it is,
+	 * as we checked above.
+	 */
+
+	return ret;
+}
+
+int wg_socket_endpoint_from_skb(struct endpoint *endpoint,
+				const struct sk_buff *skb)
+{
+	memset(endpoint, 0, sizeof(*endpoint));
+	if (skb->protocol == htons(ETH_P_IP)) {
+		endpoint->addr4.sin_family = AF_INET;
+		endpoint->addr4.sin_port = udp_hdr(skb)->source;
+		endpoint->addr4.sin_addr.s_addr = ip_hdr(skb)->saddr;
+		endpoint->src4.s_addr = ip_hdr(skb)->daddr;
+		endpoint->src_if4 = skb->skb_iif;
+	} else if (IS_ENABLED(CONFIG_IPV6) && skb->protocol == htons(ETH_P_IPV6)) {
+		endpoint->addr6.sin6_family = AF_INET6;
+		endpoint->addr6.sin6_port = udp_hdr(skb)->source;
+		endpoint->addr6.sin6_addr = ipv6_hdr(skb)->saddr;
+		endpoint->addr6.sin6_scope_id = ipv6_iface_scope_id(
+			&ipv6_hdr(skb)->saddr, skb->skb_iif);
+		endpoint->src6 = ipv6_hdr(skb)->daddr;
+	} else {
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static bool endpoint_eq(const struct endpoint *a, const struct endpoint *b)
+{
+	return (a->addr.sa_family == AF_INET && b->addr.sa_family == AF_INET &&
+		a->addr4.sin_port == b->addr4.sin_port &&
+		a->addr4.sin_addr.s_addr == b->addr4.sin_addr.s_addr &&
+		a->src4.s_addr == b->src4.s_addr && a->src_if4 == b->src_if4) ||
+	       (a->addr.sa_family == AF_INET6 &&
+		b->addr.sa_family == AF_INET6 &&
+		a->addr6.sin6_port == b->addr6.sin6_port &&
+		ipv6_addr_equal(&a->addr6.sin6_addr, &b->addr6.sin6_addr) &&
+		a->addr6.sin6_scope_id == b->addr6.sin6_scope_id &&
+		ipv6_addr_equal(&a->src6, &b->src6)) ||
+	       unlikely(!a->addr.sa_family && !b->addr.sa_family);
+}
+
+void wg_socket_set_peer_endpoint(struct wg_peer *peer,
+				 const struct endpoint *endpoint)
+{
+	/* First we check unlocked, in order to optimize, since it's pretty rare
+	 * that an endpoint will change. If we happen to be mid-write, and two
+	 * CPUs wind up writing the same thing or something slightly different,
+	 * it doesn't really matter much either.
+	 */
+	if (endpoint_eq(endpoint, &peer->endpoint))
+		return;
+	write_lock_bh(&peer->endpoint_lock);
+	if (endpoint->addr.sa_family == AF_INET) {
+		peer->endpoint.addr4 = endpoint->addr4;
+		peer->endpoint.src4 = endpoint->src4;
+		peer->endpoint.src_if4 = endpoint->src_if4;
+	} else if (IS_ENABLED(CONFIG_IPV6) && endpoint->addr.sa_family == AF_INET6) {
+		peer->endpoint.addr6 = endpoint->addr6;
+		peer->endpoint.src6 = endpoint->src6;
+	} else {
+		goto out;
+	}
+	dst_cache_reset(&peer->endpoint_cache);
+out:
+	write_unlock_bh(&peer->endpoint_lock);
+}
+
+void wg_socket_set_peer_endpoint_from_skb(struct wg_peer *peer,
+					  const struct sk_buff *skb)
+{
+	struct endpoint endpoint;
+
+	if (!wg_socket_endpoint_from_skb(&endpoint, skb))
+		wg_socket_set_peer_endpoint(peer, &endpoint);
+}
+
+void wg_socket_clear_peer_endpoint_src(struct wg_peer *peer)
+{
+	write_lock_bh(&peer->endpoint_lock);
+	memset(&peer->endpoint.src6, 0, sizeof(peer->endpoint.src6));
+	dst_cache_reset_now(&peer->endpoint_cache);
+	write_unlock_bh(&peer->endpoint_lock);
+}
+
+static int wg_receive(struct sock *sk, struct sk_buff *skb)
+{
+	struct wg_device *wg;
+
+	if (unlikely(!sk))
+		goto err;
+	wg = sk->sk_user_data;
+	if (unlikely(!wg))
+		goto err;
+	skb_mark_not_on_list(skb);
+	wg_packet_receive(wg, skb);
+	return 0;
+
+err:
+	kfree_skb(skb);
+	return 0;
+}
+
+static void sock_free(struct sock *sock)
+{
+	if (unlikely(!sock))
+		return;
+	sk_clear_memalloc(sock);
+	udp_tunnel_sock_release(sock);
+}
+
+static void set_sock_opts(struct socket *sock)
+{
+	sock->sk->sk_allocation = GFP_ATOMIC;
+	sock->sk->sk_sndbuf = INT_MAX;
+	sk_set_memalloc(sock->sk);
+}
+
+int wg_socket_init(struct wg_device *wg, u16 port)
+{
+	struct net *net;
+	int ret;
+	struct udp_tunnel_sock_cfg cfg = {
+		.sk_user_data = wg,
+		.encap_type = 1,
+		.encap_rcv = wg_receive
+	};
+	struct socket *new4 = NULL, *new6 = NULL;
+	struct udp_port_cfg port4 = {
+		.family = AF_INET,
+		.local_ip.s_addr = htonl(INADDR_ANY),
+		.local_udp_port = htons(port),
+		.use_udp_checksums = true
+	};
+#if IS_ENABLED(CONFIG_IPV6)
+	int retries = 0;
+	struct udp_port_cfg port6 = {
+		.family = AF_INET6,
+		.local_ip6 = IN6ADDR_ANY_INIT,
+		.use_udp6_tx_checksums = true,
+		.use_udp6_rx_checksums = true,
+		.ipv6_v6only = true
+	};
+#endif
+
+	rcu_read_lock();
+	net = rcu_dereference(wg->creating_net);
+	net = net ? maybe_get_net(net) : NULL;
+	rcu_read_unlock();
+	if (unlikely(!net))
+		return -ENONET;
+
+#if IS_ENABLED(CONFIG_IPV6)
+retry:
+#endif
+
+	ret = udp_sock_create(net, &port4, &new4);
+	if (ret < 0) {
+		pr_err("%s: Could not create IPv4 socket\n", wg->dev->name);
+		goto out;
+	}
+	set_sock_opts(new4);
+	setup_udp_tunnel_sock(net, new4->sk, &cfg);
+
+#if IS_ENABLED(CONFIG_IPV6)
+	if (ipv6_mod_enabled()) {
+		port6.local_udp_port = inet_sk(new4->sk)->inet_sport;
+		ret = udp_sock_create(net, &port6, &new6);
+		if (ret < 0) {
+			udp_tunnel_sock_release(new4->sk);
+			if (ret == -EADDRINUSE && !port && retries++ < 100)
+				goto retry;
+			pr_err("%s: Could not create IPv6 socket\n",
+			       wg->dev->name);
+			goto out;
+		}
+		set_sock_opts(new6);
+		setup_udp_tunnel_sock(net, new6->sk, &cfg);
+	}
+#endif
+
+	wg_socket_reinit(wg, new4->sk, new6 ? new6->sk : NULL);
+	ret = 0;
+out:
+	put_net(net);
+	return ret;
+}
+
+void wg_socket_reinit(struct wg_device *wg, struct sock *new4,
+		      struct sock *new6)
+{
+	struct sock *old4, *old6;
+
+	mutex_lock(&wg->socket_update_lock);
+	old4 = rcu_dereference_protected(wg->sock4,
+				lockdep_is_held(&wg->socket_update_lock));
+	old6 = rcu_dereference_protected(wg->sock6,
+				lockdep_is_held(&wg->socket_update_lock));
+	rcu_assign_pointer(wg->sock4, new4);
+	rcu_assign_pointer(wg->sock6, new6);
+	if (new4)
+		wg->incoming_port = ntohs(inet_sk(new4)->inet_sport);
+	mutex_unlock(&wg->socket_update_lock);
+	synchronize_net();
+	sock_free(old4);
+	sock_free(old6);
+}