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d5be7f632b
Syzkaller again found a path to a kernel crash through bad gso input. By building an excessively large packet to cause an skb field to wrap. If VIRTIO_NET_HDR_F_NEEDS_CSUM was set this would have been dropped in skb_partial_csum_set. GSO packets that do not set checksum offload are suspicious and rare. Most callers of virtio_net_hdr_to_skb already pass them to skb_probe_transport_header. Move that test forward, change it to detect parse failure and drop packets on failure as those cleary are not one of the legitimate VIRTIO_NET_HDR_GSO types. Fixes:bfd5f4a3d6("packet: Add GSO/csum offload support.") Fixes:f43798c276("tun: Allow GSO using virtio_net_hdr") Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Willem de Bruijn <willemb@google.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
126 lines
3.3 KiB
C
126 lines
3.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_VIRTIO_NET_H
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#define _LINUX_VIRTIO_NET_H
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#include <linux/if_vlan.h>
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#include <uapi/linux/virtio_net.h>
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static inline int virtio_net_hdr_set_proto(struct sk_buff *skb,
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const struct virtio_net_hdr *hdr)
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{
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switch (hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
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case VIRTIO_NET_HDR_GSO_TCPV4:
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case VIRTIO_NET_HDR_GSO_UDP:
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skb->protocol = cpu_to_be16(ETH_P_IP);
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break;
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case VIRTIO_NET_HDR_GSO_TCPV6:
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skb->protocol = cpu_to_be16(ETH_P_IPV6);
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break;
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default:
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return -EINVAL;
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}
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return 0;
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}
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static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
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const struct virtio_net_hdr *hdr,
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bool little_endian)
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{
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unsigned int gso_type = 0;
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if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
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switch (hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
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case VIRTIO_NET_HDR_GSO_TCPV4:
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gso_type = SKB_GSO_TCPV4;
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break;
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case VIRTIO_NET_HDR_GSO_TCPV6:
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gso_type = SKB_GSO_TCPV6;
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break;
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case VIRTIO_NET_HDR_GSO_UDP:
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gso_type = SKB_GSO_UDP;
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break;
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default:
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return -EINVAL;
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}
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if (hdr->gso_type & VIRTIO_NET_HDR_GSO_ECN)
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gso_type |= SKB_GSO_TCP_ECN;
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if (hdr->gso_size == 0)
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return -EINVAL;
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}
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if (hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
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u16 start = __virtio16_to_cpu(little_endian, hdr->csum_start);
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u16 off = __virtio16_to_cpu(little_endian, hdr->csum_offset);
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if (!skb_partial_csum_set(skb, start, off))
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return -EINVAL;
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} else {
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/* gso packets without NEEDS_CSUM do not set transport_offset.
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* probe and drop if does not match one of the above types.
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*/
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if (gso_type) {
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skb_probe_transport_header(skb, -1);
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if (!skb_transport_header_was_set(skb))
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return -EINVAL;
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}
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}
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if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
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u16 gso_size = __virtio16_to_cpu(little_endian, hdr->gso_size);
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skb_shinfo(skb)->gso_size = gso_size;
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skb_shinfo(skb)->gso_type = gso_type;
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/* Header must be checked, and gso_segs computed. */
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skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
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skb_shinfo(skb)->gso_segs = 0;
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}
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return 0;
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}
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static inline int virtio_net_hdr_from_skb(const struct sk_buff *skb,
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struct virtio_net_hdr *hdr,
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bool little_endian,
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bool has_data_valid,
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int vlan_hlen)
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{
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memset(hdr, 0, sizeof(*hdr)); /* no info leak */
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if (skb_is_gso(skb)) {
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struct skb_shared_info *sinfo = skb_shinfo(skb);
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/* This is a hint as to how much should be linear. */
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hdr->hdr_len = __cpu_to_virtio16(little_endian,
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skb_headlen(skb));
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hdr->gso_size = __cpu_to_virtio16(little_endian,
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sinfo->gso_size);
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if (sinfo->gso_type & SKB_GSO_TCPV4)
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hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
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else if (sinfo->gso_type & SKB_GSO_TCPV6)
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hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
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else
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return -EINVAL;
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if (sinfo->gso_type & SKB_GSO_TCP_ECN)
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hdr->gso_type |= VIRTIO_NET_HDR_GSO_ECN;
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} else
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hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
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if (skb->ip_summed == CHECKSUM_PARTIAL) {
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hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
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hdr->csum_start = __cpu_to_virtio16(little_endian,
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skb_checksum_start_offset(skb) + vlan_hlen);
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hdr->csum_offset = __cpu_to_virtio16(little_endian,
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skb->csum_offset);
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} else if (has_data_valid &&
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skb->ip_summed == CHECKSUM_UNNECESSARY) {
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hdr->flags = VIRTIO_NET_HDR_F_DATA_VALID;
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} /* else everything is zero */
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return 0;
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}
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#endif /* _LINUX_VIRTIO_NET_H */
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