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, 645 insertions, 0 deletions

diff --git a/net/ipv4/ip_options.c b/net/ipv4/ip_options.c
new file mode 100644
index 000000000..09d745112
--- /dev/null
+++ b/net/ipv4/ip_options.c
@@ -0,0 +1,645 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * INET		An implementation of the TCP/IP protocol suite for the LINUX
+ *		operating system.  INET is implemented using the  BSD Socket
+ *		interface as the means of communication with the user level.
+ *
+ *		The options processing module for ip.c
+ *
+ * Authors:	A.N.Kuznetsov
+ *
+ */
+
+#define pr_fmt(fmt) "IPv4: " fmt
+
+#include <linux/capability.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/uaccess.h>
+#include <linux/unaligned.h>
+#include <linux/skbuff.h>
+#include <linux/ip.h>
+#include <linux/icmp.h>
+#include <linux/netdevice.h>
+#include <linux/rtnetlink.h>
+#include <net/sock.h>
+#include <net/ip.h>
+#include <net/icmp.h>
+#include <net/route.h>
+#include <net/cipso_ipv4.h>
+#include <net/ip_fib.h>
+
+/*
+ * Write options to IP header, record destination address to
+ * source route option, address of outgoing interface
+ * (we should already know it, so that this  function is allowed be
+ * called only after routing decision) and timestamp,
+ * if we originate this datagram.
+ *
+ * daddr is real destination address, next hop is recorded in IP header.
+ * saddr is address of outgoing interface.
+ */
+
+void ip_options_build(struct sk_buff *skb, struct ip_options *opt,
+		      __be32 daddr, struct rtable *rt)
+{
+	unsigned char *iph = skb_network_header(skb);
+
+	memcpy(&(IPCB(skb)->opt), opt, sizeof(struct ip_options));
+	memcpy(iph + sizeof(struct iphdr), opt->__data, opt->optlen);
+	opt = &(IPCB(skb)->opt);
+
+	if (opt->srr)
+		memcpy(iph + opt->srr + iph[opt->srr + 1] - 4, &daddr, 4);
+
+	if (opt->rr_needaddr)
+		ip_rt_get_source(iph + opt->rr + iph[opt->rr + 2] - 5, skb, rt);
+	if (opt->ts_needaddr)
+		ip_rt_get_source(iph + opt->ts + iph[opt->ts + 2] - 9, skb, rt);
+	if (opt->ts_needtime) {
+		__be32 midtime;
+
+		midtime = inet_current_timestamp();
+		memcpy(iph + opt->ts + iph[opt->ts + 2] - 5, &midtime, 4);
+	}
+}
+
+/*
+ * Provided (sopt, skb) points to received options,
+ * build in dopt compiled option set appropriate for answering.
+ * i.e. invert SRR option, copy anothers,
+ * and grab room in RR/TS options.
+ *
+ * NOTE: dopt cannot point to skb.
+ */
+
+int __ip_options_echo(struct net *net, struct ip_options *dopt,
+		      struct sk_buff *skb, const struct ip_options *sopt)
+{
+	unsigned char *sptr, *dptr;
+	int soffset, doffset;
+	int	optlen;
+
+	memset(dopt, 0, sizeof(struct ip_options));
+
+	if (sopt->optlen == 0)
+		return 0;
+
+	sptr = skb_network_header(skb);
+	dptr = dopt->__data;
+
+	if (sopt->rr) {
+		optlen  = sptr[sopt->rr+1];
+		soffset = sptr[sopt->rr+2];
+		dopt->rr = dopt->optlen + sizeof(struct iphdr);
+		memcpy(dptr, sptr+sopt->rr, optlen);
+		if (sopt->rr_needaddr && soffset <= optlen) {
+			if (soffset + 3 > optlen)
+				return -EINVAL;
+			dptr[2] = soffset + 4;
+			dopt->rr_needaddr = 1;
+		}
+		dptr += optlen;
+		dopt->optlen += optlen;
+	}
+	if (sopt->ts) {
+		optlen = sptr[sopt->ts+1];
+		soffset = sptr[sopt->ts+2];
+		dopt->ts = dopt->optlen + sizeof(struct iphdr);
+		memcpy(dptr, sptr+sopt->ts, optlen);
+		if (soffset <= optlen) {
+			if (sopt->ts_needaddr) {
+				if (soffset + 3 > optlen)
+					return -EINVAL;
+				dopt->ts_needaddr = 1;
+				soffset += 4;
+			}
+			if (sopt->ts_needtime) {
+				if (soffset + 3 > optlen)
+					return -EINVAL;
+				if ((dptr[3]&0xF) != IPOPT_TS_PRESPEC) {
+					dopt->ts_needtime = 1;
+					soffset += 4;
+				} else {
+					dopt->ts_needtime = 0;
+
+					if (soffset + 7 <= optlen) {
+						__be32 addr;
+
+						memcpy(&addr, dptr+soffset-1, 4);
+						if (inet_addr_type(net, addr) != RTN_UNICAST) {
+							dopt->ts_needtime = 1;
+							soffset += 8;
+						}
+					}
+				}
+			}
+			dptr[2] = soffset;
+		}
+		dptr += optlen;
+		dopt->optlen += optlen;
+	}
+	if (sopt->srr) {
+		unsigned char *start = sptr+sopt->srr;
+		__be32 faddr;
+
+		optlen  = start[1];
+		soffset = start[2];
+		doffset = 0;
+		if (soffset > optlen)
+			soffset = optlen + 1;
+		soffset -= 4;
+		if (soffset > 3) {
+			memcpy(&faddr, &start[soffset-1], 4);
+			for (soffset -= 4, doffset = 4; soffset > 3; soffset -= 4, doffset += 4)
+				memcpy(&dptr[doffset-1], &start[soffset-1], 4);
+			/*
+			 * RFC1812 requires to fix illegal source routes.
+			 */
+			if (memcmp(&ip_hdr(skb)->saddr,
+				   &start[soffset + 3], 4) == 0)
+				doffset -= 4;
+		}
+		if (doffset > 3) {
+			dopt->faddr = faddr;
+			dptr[0] = start[0];
+			dptr[1] = doffset+3;
+			dptr[2] = 4;
+			dptr += doffset+3;
+			dopt->srr = dopt->optlen + sizeof(struct iphdr);
+			dopt->optlen += doffset+3;
+			dopt->is_strictroute = sopt->is_strictroute;
+		}
+	}
+	if (sopt->cipso) {
+		optlen  = sptr[sopt->cipso+1];
+		dopt->cipso = dopt->optlen+sizeof(struct iphdr);
+		memcpy(dptr, sptr+sopt->cipso, optlen);
+		dptr += optlen;
+		dopt->optlen += optlen;
+	}
+	while (dopt->optlen & 3) {
+		*dptr++ = IPOPT_END;
+		dopt->optlen++;
+	}
+	return 0;
+}
+
+/*
+ *	Options "fragmenting", just fill options not
+ *	allowed in fragments with NOOPs.
+ *	Simple and stupid 8), but the most efficient way.
+ */
+
+void ip_options_fragment(struct sk_buff *skb)
+{
+	unsigned char *optptr = skb_network_header(skb) + sizeof(struct iphdr);
+	struct ip_options *opt = &(IPCB(skb)->opt);
+	int  l = opt->optlen;
+	int  optlen;
+
+	while (l > 0) {
+		switch (*optptr) {
+		case IPOPT_END:
+			return;
+		case IPOPT_NOOP:
+			l--;
+			optptr++;
+			continue;
+		}
+		optlen = optptr[1];
+		if (optlen < 2 || optlen > l)
+		  return;
+		if (!IPOPT_COPIED(*optptr))
+			memset(optptr, IPOPT_NOOP, optlen);
+		l -= optlen;
+		optptr += optlen;
+	}
+	opt->ts = 0;
+	opt->rr = 0;
+	opt->rr_needaddr = 0;
+	opt->ts_needaddr = 0;
+	opt->ts_needtime = 0;
+}
+
+/* helper used by ip_options_compile() to call fib_compute_spec_dst()
+ * at most one time.
+ */
+static void spec_dst_fill(__be32 *spec_dst, struct sk_buff *skb)
+{
+	if (*spec_dst == htonl(INADDR_ANY))
+		*spec_dst = fib_compute_spec_dst(skb);
+}
+
+/*
+ * Verify options and fill pointers in struct options.
+ * Caller should clear *opt, and set opt->data.
+ * If opt == NULL, then skb->data should point to IP header.
+ */
+
+int __ip_options_compile(struct net *net,
+			 struct ip_options *opt, struct sk_buff *skb,
+			 __be32 *info)
+{
+	__be32 spec_dst = htonl(INADDR_ANY);
+	unsigned char *pp_ptr = NULL;
+	struct rtable *rt = NULL;
+	unsigned char *optptr;
+	unsigned char *iph;
+	int optlen, l;
+
+	if (skb) {
+		rt = skb_rtable(skb);
+		optptr = (unsigned char *)&(ip_hdr(skb)[1]);
+	} else
+		optptr = opt->__data;
+	iph = optptr - sizeof(struct iphdr);
+
+	for (l = opt->optlen; l > 0; ) {
+		switch (*optptr) {
+		case IPOPT_END:
+			for (optptr++, l--; l > 0; optptr++, l--) {
+				if (*optptr != IPOPT_END) {
+					*optptr = IPOPT_END;
+					opt->is_changed = 1;
+				}
+			}
+			goto eol;
+		case IPOPT_NOOP:
+			l--;
+			optptr++;
+			continue;
+		}
+		if (unlikely(l < 2)) {
+			pp_ptr = optptr;
+			goto error;
+		}
+		optlen = optptr[1];
+		if (optlen < 2 || optlen > l) {
+			pp_ptr = optptr;
+			goto error;
+		}
+		switch (*optptr) {
+		case IPOPT_SSRR:
+		case IPOPT_LSRR:
+			if (optlen < 3) {
+				pp_ptr = optptr + 1;
+				goto error;
+			}
+			if (optptr[2] < 4) {
+				pp_ptr = optptr + 2;
+				goto error;
+			}
+			/* NB: cf RFC-1812 5.2.4.1 */
+			if (opt->srr) {
+				pp_ptr = optptr;
+				goto error;
+			}
+			if (!skb) {
+				if (optptr[2] != 4 || optlen < 7 || ((optlen-3) & 3)) {
+					pp_ptr = optptr + 1;
+					goto error;
+				}
+				memcpy(&opt->faddr, &optptr[3], 4);
+				if (optlen > 7)
+					memmove(&optptr[3], &optptr[7], optlen-7);
+			}
+			opt->is_strictroute = (optptr[0] == IPOPT_SSRR);
+			opt->srr = optptr - iph;
+			break;
+		case IPOPT_RR:
+			if (opt->rr) {
+				pp_ptr = optptr;
+				goto error;
+			}
+			if (optlen < 3) {
+				pp_ptr = optptr + 1;
+				goto error;
+			}
+			if (optptr[2] < 4) {
+				pp_ptr = optptr + 2;
+				goto error;
+			}
+			if (optptr[2] <= optlen) {
+				if (optptr[2]+3 > optlen) {
+					pp_ptr = optptr + 2;
+					goto error;
+				}
+				if (rt) {
+					spec_dst_fill(&spec_dst, skb);
+					memcpy(&optptr[optptr[2]-1], &spec_dst, 4);
+					opt->is_changed = 1;
+				}
+				optptr[2] += 4;
+				opt->rr_needaddr = 1;
+			}
+			opt->rr = optptr - iph;
+			break;
+		case IPOPT_TIMESTAMP:
+			if (opt->ts) {
+				pp_ptr = optptr;
+				goto error;
+			}
+			if (optlen < 4) {
+				pp_ptr = optptr + 1;
+				goto error;
+			}
+			if (optptr[2] < 5) {
+				pp_ptr = optptr + 2;
+				goto error;
+			}
+			if (optptr[2] <= optlen) {
+				unsigned char *timeptr = NULL;
+				if (optptr[2]+3 > optlen) {
+					pp_ptr = optptr + 2;
+					goto error;
+				}
+				switch (optptr[3]&0xF) {
+				case IPOPT_TS_TSONLY:
+					if (skb)
+						timeptr = &optptr[optptr[2]-1];
+					opt->ts_needtime = 1;
+					optptr[2] += 4;
+					break;
+				case IPOPT_TS_TSANDADDR:
+					if (optptr[2]+7 > optlen) {
+						pp_ptr = optptr + 2;
+						goto error;
+					}
+					if (rt)  {
+						spec_dst_fill(&spec_dst, skb);
+						memcpy(&optptr[optptr[2]-1], &spec_dst, 4);
+						timeptr = &optptr[optptr[2]+3];
+					}
+					opt->ts_needaddr = 1;
+					opt->ts_needtime = 1;
+					optptr[2] += 8;
+					break;
+				case IPOPT_TS_PRESPEC:
+					if (optptr[2]+7 > optlen) {
+						pp_ptr = optptr + 2;
+						goto error;
+					}
+					{
+						__be32 addr;
+						memcpy(&addr, &optptr[optptr[2]-1], 4);
+						if (inet_addr_type(net, addr) == RTN_UNICAST)
+							break;
+						if (skb)
+							timeptr = &optptr[optptr[2]+3];
+					}
+					opt->ts_needtime = 1;
+					optptr[2] += 8;
+					break;
+				default:
+					if (!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) {
+						pp_ptr = optptr + 3;
+						goto error;
+					}
+					break;
+				}
+				if (timeptr) {
+					__be32 midtime;
+
+					midtime = inet_current_timestamp();
+					memcpy(timeptr, &midtime, 4);
+					opt->is_changed = 1;
+				}
+			} else if ((optptr[3]&0xF) != IPOPT_TS_PRESPEC) {
+				unsigned int overflow = optptr[3]>>4;
+				if (overflow == 15) {
+					pp_ptr = optptr + 3;
+					goto error;
+				}
+				if (skb) {
+					optptr[3] = (optptr[3]&0xF)|((overflow+1)<<4);
+					opt->is_changed = 1;
+				}
+			}
+			opt->ts = optptr - iph;
+			break;
+		case IPOPT_RA:
+			if (optlen < 4) {
+				pp_ptr = optptr + 1;
+				goto error;
+			}
+			if (optptr[2] == 0 && optptr[3] == 0)
+				opt->router_alert = optptr - iph;
+			break;
+		case IPOPT_CIPSO:
+			if ((!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) || opt->cipso) {
+				pp_ptr = optptr;
+				goto error;
+			}
+			opt->cipso = optptr - iph;
+			if (cipso_v4_validate(skb, &optptr)) {
+				pp_ptr = optptr;
+				goto error;
+			}
+			break;
+		case IPOPT_SEC:
+		case IPOPT_SID:
+		default:
+			if (!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) {
+				pp_ptr = optptr;
+				goto error;
+			}
+			break;
+		}
+		l -= optlen;
+		optptr += optlen;
+	}
+
+eol:
+	if (!pp_ptr)
+		return 0;
+
+error:
+	if (info)
+		*info = htonl((pp_ptr-iph)<<24);
+	return -EINVAL;
+}
+EXPORT_SYMBOL(__ip_options_compile);
+
+int ip_options_compile(struct net *net,
+		       struct ip_options *opt, struct sk_buff *skb)
+{
+	int ret;
+	__be32 info;
+
+	ret = __ip_options_compile(net, opt, skb, &info);
+	if (ret != 0 && skb)
+		icmp_send(skb, ICMP_PARAMETERPROB, 0, info);
+	return ret;
+}
+EXPORT_SYMBOL(ip_options_compile);
+
+/*
+ *	Undo all the changes done by ip_options_compile().
+ */
+
+void ip_options_undo(struct ip_options *opt)
+{
+	if (opt->srr) {
+		unsigned char *optptr = opt->__data + opt->srr - sizeof(struct iphdr);
+
+		memmove(optptr + 7, optptr + 3, optptr[1] - 7);
+		memcpy(optptr + 3, &opt->faddr, 4);
+	}
+	if (opt->rr_needaddr) {
+		unsigned char *optptr = opt->__data + opt->rr - sizeof(struct iphdr);
+
+		optptr[2] -= 4;
+		memset(&optptr[optptr[2] - 1], 0, 4);
+	}
+	if (opt->ts) {
+		unsigned char *optptr = opt->__data + opt->ts - sizeof(struct iphdr);
+
+		if (opt->ts_needtime) {
+			optptr[2] -= 4;
+			memset(&optptr[optptr[2] - 1], 0, 4);
+			if ((optptr[3] & 0xF) == IPOPT_TS_PRESPEC)
+				optptr[2] -= 4;
+		}
+		if (opt->ts_needaddr) {
+			optptr[2] -= 4;
+			memset(&optptr[optptr[2] - 1], 0, 4);
+		}
+	}
+}
+
+int ip_options_get(struct net *net, struct ip_options_rcu **optp,
+		   sockptr_t data, int optlen)
+{
+	struct ip_options_rcu *opt;
+
+	opt = kzalloc(sizeof(struct ip_options_rcu) + ((optlen + 3) & ~3),
+		       GFP_KERNEL);
+	if (!opt)
+		return -ENOMEM;
+	if (optlen && copy_from_sockptr(opt->opt.__data, data, optlen)) {
+		kfree(opt);
+		return -EFAULT;
+	}
+
+	while (optlen & 3)
+		opt->opt.__data[optlen++] = IPOPT_END;
+	opt->opt.optlen = optlen;
+	if (optlen && ip_options_compile(net, &opt->opt, NULL)) {
+		kfree(opt);
+		return -EINVAL;
+	}
+	if (opt->opt.srr && !ns_capable(net->user_ns, CAP_NET_RAW)) {
+		kfree(opt);
+		return -EPERM;
+	}
+	kfree(*optp);
+	*optp = opt;
+	return 0;
+}
+
+void ip_forward_options(struct sk_buff *skb)
+{
+	struct   ip_options *opt	= &(IPCB(skb)->opt);
+	unsigned char *optptr;
+	struct rtable *rt = skb_rtable(skb);
+	unsigned char *raw = skb_network_header(skb);
+
+	if (opt->rr_needaddr) {
+		optptr = (unsigned char *)raw + opt->rr;
+		ip_rt_get_source(&optptr[optptr[2]-5], skb, rt);
+		opt->is_changed = 1;
+	}
+	if (opt->srr_is_hit) {
+		int srrptr, srrspace;
+
+		optptr = raw + opt->srr;
+
+		for ( srrptr = optptr[2], srrspace = optptr[1];
+		     srrptr <= srrspace;
+		     srrptr += 4
+		     ) {
+			if (srrptr + 3 > srrspace)
+				break;
+			if (memcmp(&opt->nexthop, &optptr[srrptr-1], 4) == 0)
+				break;
+		}
+		if (srrptr + 3 <= srrspace) {
+			opt->is_changed = 1;
+			ip_hdr(skb)->daddr = opt->nexthop;
+			ip_rt_get_source(&optptr[srrptr-1], skb, rt);
+			optptr[2] = srrptr+4;
+		} else {
+			net_crit_ratelimited("%s(): Argh! Destination lost!\n",
+					     __func__);
+		}
+		if (opt->ts_needaddr) {
+			optptr = raw + opt->ts;
+			ip_rt_get_source(&optptr[optptr[2]-9], skb, rt);
+			opt->is_changed = 1;
+		}
+	}
+	if (opt->is_changed) {
+		opt->is_changed = 0;
+		ip_send_check(ip_hdr(skb));
+	}
+}
+
+int ip_options_rcv_srr(struct sk_buff *skb, struct net_device *dev)
+{
+	struct ip_options *opt = &(IPCB(skb)->opt);
+	int srrspace, srrptr;
+	__be32 nexthop;
+	struct iphdr *iph = ip_hdr(skb);
+	unsigned char *optptr = skb_network_header(skb) + opt->srr;
+	struct rtable *rt = skb_rtable(skb);
+	struct rtable *rt2;
+	unsigned long orefdst;
+	int err;
+
+	if (!rt)
+		return 0;
+
+	if (skb->pkt_type != PACKET_HOST)
+		return -EINVAL;
+	if (rt->rt_type == RTN_UNICAST) {
+		if (!opt->is_strictroute)
+			return 0;
+		icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl(16<<24));
+		return -EINVAL;
+	}
+	if (rt->rt_type != RTN_LOCAL)
+		return -EINVAL;
+
+	for (srrptr = optptr[2], srrspace = optptr[1]; srrptr <= srrspace; srrptr += 4) {
+		if (srrptr + 3 > srrspace) {
+			icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((opt->srr+2)<<24));
+			return -EINVAL;
+		}
+		memcpy(&nexthop, &optptr[srrptr-1], 4);
+
+		orefdst = skb_dstref_steal(skb);
+		err = ip_route_input(skb, nexthop, iph->saddr, ip4h_dscp(iph),
+				     dev) ? -EINVAL : 0;
+		rt2 = skb_rtable(skb);
+		if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) {
+			skb_dst_drop(skb);
+			skb_dstref_restore(skb, orefdst);
+			return -EINVAL;
+		}
+		refdst_drop(orefdst);
+		if (rt2->rt_type != RTN_LOCAL)
+			break;
+		/* Superfast 8) loopback forward */
+		iph->daddr = nexthop;
+		opt->is_changed = 1;
+	}
+	if (srrptr <= srrspace) {
+		opt->srr_is_hit = 1;
+		opt->nexthop = nexthop;
+		opt->is_changed = 1;
+	}
+	return 0;
+}
+EXPORT_SYMBOL(ip_options_rcv_srr);