Revision 0447378a4a793da008451fad50bc0f93e9675ae6 authored by Marc Orr on 21 June 2018, 00:21:29 UTC, committed by Radim Krčmář on 22 June 2018, 14:46:26 UTC
This patch extends the checks done prior to a nested VM entry.
Specifically, it extends the check_vmentry_prereqs function with checks
for fields relevant to the VM-entry event injection information, as
described in the Intel SDM, volume 3.

This patch is motivated by a syzkaller bug, where a bad VM-entry
interruption information field is generated in the VMCS02, which causes
the nested VM launch to fail. Then, KVM fails to resume L1.

While KVM should be improved to correctly resume L1 execution after a
failed nested launch, this change is justified because the existing code
to resume L1 is flaky/ad-hoc and the test coverage for resuming L1 is
sparse.

Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Marc Orr <marcorr@google.com>
[Removed comment whose parts were describing previous revisions and the
 rest was obvious from function/variable naming. - Radim]
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
1 parent 5f9077c
Raw File
tso.c
// SPDX-License-Identifier: GPL-2.0
#include <linux/export.h>
#include <linux/if_vlan.h>
#include <net/ip.h>
#include <net/tso.h>
#include <asm/unaligned.h>

/* Calculate expected number of TX descriptors */
int tso_count_descs(struct sk_buff *skb)
{
	/* The Marvell Way */
	return skb_shinfo(skb)->gso_segs * 2 + skb_shinfo(skb)->nr_frags;
}
EXPORT_SYMBOL(tso_count_descs);

void tso_build_hdr(struct sk_buff *skb, char *hdr, struct tso_t *tso,
		   int size, bool is_last)
{
	struct tcphdr *tcph;
	int hdr_len = skb_transport_offset(skb) + tcp_hdrlen(skb);
	int mac_hdr_len = skb_network_offset(skb);

	memcpy(hdr, skb->data, hdr_len);
	if (!tso->ipv6) {
		struct iphdr *iph = (void *)(hdr + mac_hdr_len);

		iph->id = htons(tso->ip_id);
		iph->tot_len = htons(size + hdr_len - mac_hdr_len);
		tso->ip_id++;
	} else {
		struct ipv6hdr *iph = (void *)(hdr + mac_hdr_len);

		iph->payload_len = htons(size + tcp_hdrlen(skb));
	}
	tcph = (struct tcphdr *)(hdr + skb_transport_offset(skb));
	put_unaligned_be32(tso->tcp_seq, &tcph->seq);

	if (!is_last) {
		/* Clear all special flags for not last packet */
		tcph->psh = 0;
		tcph->fin = 0;
		tcph->rst = 0;
	}
}
EXPORT_SYMBOL(tso_build_hdr);

void tso_build_data(struct sk_buff *skb, struct tso_t *tso, int size)
{
	tso->tcp_seq += size;
	tso->size -= size;
	tso->data += size;

	if ((tso->size == 0) &&
	    (tso->next_frag_idx < skb_shinfo(skb)->nr_frags)) {
		skb_frag_t *frag = &skb_shinfo(skb)->frags[tso->next_frag_idx];

		/* Move to next segment */
		tso->size = frag->size;
		tso->data = page_address(frag->page.p) + frag->page_offset;
		tso->next_frag_idx++;
	}
}
EXPORT_SYMBOL(tso_build_data);

void tso_start(struct sk_buff *skb, struct tso_t *tso)
{
	int hdr_len = skb_transport_offset(skb) + tcp_hdrlen(skb);

	tso->ip_id = ntohs(ip_hdr(skb)->id);
	tso->tcp_seq = ntohl(tcp_hdr(skb)->seq);
	tso->next_frag_idx = 0;
	tso->ipv6 = vlan_get_protocol(skb) == htons(ETH_P_IPV6);

	/* Build first data */
	tso->size = skb_headlen(skb) - hdr_len;
	tso->data = skb->data + hdr_len;
	if ((tso->size == 0) &&
	    (tso->next_frag_idx < skb_shinfo(skb)->nr_frags)) {
		skb_frag_t *frag = &skb_shinfo(skb)->frags[tso->next_frag_idx];

		/* Move to next segment */
		tso->size = frag->size;
		tso->data = page_address(frag->page.p) + frag->page_offset;
		tso->next_frag_idx++;
	}
}
EXPORT_SYMBOL(tso_start);
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