From dfab3bad4732c4b97347421a0a3a4c690e912be4 Mon Sep 17 00:00:00 2001 From: Paulos Yibelo Date: Mon, 21 Sep 2026 19:38:51 -0400 Subject: [PATCH net v6 1/2] net: validate virtio checksum start after network header __virtio_net_hdr_to_skb() checks a minimum network-header length for CHECKSUM_PARTIAL packets. Its checksum start is relative to skb->data, but some callers have not established skb->network_header when they convert the virtio header. Pass the data-relative L3 origin explicitly. Ethernet receive paths parse the frame and nested VLAN headers without changing skb state. AF_PACKET uses the frame's actual L3 origin even when the socket protocol is ETH_P_IP and the raw frame carries VLAN tags. Non-Ethernet AF_PACKET devices retain their established skb network offset. Also pass the actual L3 protocol so IPv6 packets use the 40-byte base header minimum even without TCPv6 GSO. IFF_TUN obtains that protocol from the packet before skb->protocol is set. Name the Ethernet parser accordingly, use the same origin for tunnel validation, and propagate conversion failures in UML. The bound remains a minimum; fragmentation paths separately validate the parsed IPv4 or IPv6 header length before completing a checksum. Fixes: 49d14b54a527 ("net: test for not too small csum_start in virtio_net_hdr_to_skb()") Fixes: a2fb4bc4e2a6 ("net: implement virtio helpers to handle UDP GSO tunneling.") Reported-by: Paulos Yibelo Link: https://lore.kernel.org/netdev/20260920004733.6473-2-habte.yibelo@gmail.com/ Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Paulos Yibelo --- arch/um/drivers/vector_transports.c | 13 ++++- drivers/net/tun_vnet.h | 52 ++++++++++++++++- drivers/net/virtio_net.c | 10 +++- include/linux/virtio_net.h | 87 ++++++++++++++++++++++++----- net/packet/af_packet.c | 24 +++++++- 5 files changed, 163 insertions(+), 23 deletions(-) diff --git a/arch/um/drivers/vector_transports.c b/arch/um/drivers/vector_transports.c index ddd127ee9..5a9d8f49a 100644 --- a/arch/um/drivers/vector_transports.c +++ b/arch/um/drivers/vector_transports.c @@ -197,6 +197,8 @@ static int raw_verify_header( uint8_t *header, struct sk_buff *skb, struct vector_private *vp) { struct virtio_net_hdr *vheader = (struct virtio_net_hdr *) header; + __be16 network_protocol; + int network_offset; if ((vheader->gso_type != VIRTIO_NET_HDR_GSO_NONE) && (vp->req_size != 65536)) { @@ -209,8 +211,14 @@ static int raw_verify_header( if ((vheader->flags & VIRTIO_NET_HDR_F_DATA_VALID) > 0) return 1; - virtio_net_hdr_to_skb(skb, vheader, virtio_legacy_is_little_endian()); - return 0; + network_offset = virtio_net_hdr_eth_get_l3_offset(skb, vheader, + &network_protocol); + if (network_offset < 0) + return network_offset; + + return virtio_net_hdr_to_skb(skb, vheader, + virtio_legacy_is_little_endian(), + network_offset, network_protocol); } static bool get_uint_param( @@ -491,4 +499,3 @@ int build_transport_data(struct vector_private *vp) return build_bess_transport_data(vp); return 0; } - diff --git a/drivers/net/tun_vnet.h b/drivers/net/tun_vnet.h index f4c652b1f..e004213fa 100644 --- a/drivers/net/tun_vnet.h +++ b/drivers/net/tun_vnet.h @@ -177,10 +177,49 @@ static inline int tun_vnet_hdr_put(int sz, struct iov_iter *iter, return __tun_vnet_hdr_put(sz, 0, iter, hdr); } +static inline int +tun_vnet_hdr_get_l3_offset(unsigned int flags, const struct sk_buff *skb, + const struct virtio_net_hdr *hdr, + __be16 *network_protocol) +{ + if ((flags & TUN_TYPE_MASK) != IFF_TAP) { + u8 version, first_byte; + const u8 *first; + + *network_protocol = 0; + if (!(hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM)) + return 0; + + first = skb_header_pointer(skb, 0, sizeof(first_byte), + &first_byte); + if (!first) + return -EINVAL; + + version = *first >> 4; + if (version == 4) + *network_protocol = htons(ETH_P_IP); + else if (version == 6) + *network_protocol = htons(ETH_P_IPV6); + return 0; + } + + return virtio_net_hdr_eth_get_l3_offset(skb, hdr, + network_protocol); +} + static inline int tun_vnet_hdr_to_skb(unsigned int flags, struct sk_buff *skb, const struct virtio_net_hdr *hdr) { - return virtio_net_hdr_to_skb(skb, hdr, tun_vnet_is_little_endian(flags)); + __be16 network_protocol; + int network_offset = tun_vnet_hdr_get_l3_offset(flags, skb, hdr, + &network_protocol); + + if (network_offset < 0) + return network_offset; + + return virtio_net_hdr_to_skb(skb, hdr, + tun_vnet_is_little_endian(flags), + network_offset, network_protocol); } /* @@ -199,10 +238,19 @@ tun_vnet_hdr_tnl_to_skb(unsigned int flags, netdev_features_t features, struct sk_buff *skb, const struct virtio_net_hdr_v1_hash_tunnel *hdr) { + const struct virtio_net_hdr *vnet_hdr = (const struct virtio_net_hdr *)hdr; + __be16 network_protocol; + int network_offset = tun_vnet_hdr_get_l3_offset(flags, skb, vnet_hdr, + &network_protocol); + + if (network_offset < 0) + return network_offset; + return virtio_net_hdr_tnl_to_skb(skb, hdr, features & NETIF_F_GSO_UDP_TUNNEL, features & NETIF_F_GSO_UDP_TUNNEL_CSUM, - tun_vnet_is_little_endian(flags)); + tun_vnet_is_little_endian(flags), + network_offset, network_protocol); } static inline int tun_vnet_hdr_from_skb(unsigned int flags, diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index e34c52d05..8e93dad28 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -2502,6 +2502,8 @@ static void virtnet_receive_done(struct virtnet_info *vi, struct receive_queue * { struct virtio_net_common_hdr *hdr; struct net_device *dev = vi->dev; + __be16 network_protocol; + int network_offset; hdr = skb_vnet_common_hdr(skb); if (dev->features & NETIF_F_RXHASH && vi->has_rss_hash_report) @@ -2515,9 +2517,13 @@ static void virtnet_receive_done(struct virtnet_info *vi, struct receive_queue * goto frame_err; } - if (virtio_net_hdr_tnl_to_skb(skb, &hdr->tnl_hdr, vi->rx_tnl, + network_offset = virtio_net_hdr_eth_get_l3_offset(skb, &hdr->hdr, + &network_protocol); + if (network_offset < 0 || + virtio_net_hdr_tnl_to_skb(skb, &hdr->tnl_hdr, vi->rx_tnl, vi->rx_tnl_csum, - virtio_is_little_endian(vi->vdev))) { + virtio_is_little_endian(vi->vdev), + network_offset, network_protocol)) { net_warn_ratelimited("%s: bad gso: type: %x, size: %u, flags %x tunnel %d tnl csum %d\n", dev->name, hdr->hdr.gso_type, hdr->hdr.gso_size, hdr->hdr.flags, diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h index c381b916c..b89d821a0 100644 --- a/include/linux/virtio_net.h +++ b/include/linux/virtio_net.h @@ -48,16 +48,61 @@ static inline int virtio_net_hdr_set_proto(struct sk_buff *skb, return 0; } +/* + * Return the L3 offset and protocol of an Ethernet frame starting at skb->data. + * The offset is unused without NEEDS_CSUM, so avoid parsing and return zero. + */ +static inline int +virtio_net_hdr_eth_get_l3_offset(const struct sk_buff *skb, + const struct virtio_net_hdr *hdr, + __be16 *network_protocol) +{ + unsigned int parse_depth = VLAN_MAX_DEPTH; + const struct ethhdr *eth; + struct ethhdr ethbuf; + __be16 protocol; + int depth = ETH_HLEN; + + *network_protocol = 0; + if (!(hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM)) + return 0; + + eth = skb_header_pointer(skb, 0, sizeof(ethbuf), ðbuf); + if (!eth) + return -EINVAL; + + protocol = eth->h_proto; + while (eth_type_vlan(protocol)) { + const struct vlan_hdr *vh; + struct vlan_hdr vhdr; + + vh = skb_header_pointer(skb, depth, sizeof(vhdr), &vhdr); + if (!vh || !--parse_depth) + return -EINVAL; + + protocol = vh->h_vlan_encapsulated_proto; + depth += VLAN_HLEN; + } + + *network_protocol = protocol; + return depth; +} + static inline int __virtio_net_hdr_to_skb(struct sk_buff *skb, const struct virtio_net_hdr *hdr, - bool little_endian, u8 hdr_gso_type) + bool little_endian, u8 hdr_gso_type, + int network_offset, + __be16 network_protocol) { - unsigned int nh_min_len = sizeof(struct iphdr); + int nh_min_len = sizeof(struct iphdr); unsigned int gso_type = 0; unsigned int thlen = 0; unsigned int p_off = 0; unsigned int ip_proto; + if (network_protocol == htons(ETH_P_IPV6)) + nh_min_len = sizeof(struct ipv6hdr); + if (hdr_gso_type != VIRTIO_NET_HDR_GSO_NONE) { switch (hdr_gso_type & ~VIRTIO_NET_HDR_GSO_ECN) { case VIRTIO_NET_HDR_GSO_TCPV4: @@ -98,16 +143,20 @@ static inline int __virtio_net_hdr_to_skb(struct sk_buff *skb, u32 start = __virtio16_to_cpu(little_endian, hdr->csum_start); u32 off = __virtio16_to_cpu(little_endian, hdr->csum_offset); u32 needed = start + max_t(u32, thlen, off + sizeof(__sum16)); + int transport_offset; if (!pskb_may_pull(skb, needed)) return -EINVAL; if (!skb_partial_csum_set(skb, start, off)) return -EINVAL; - if (skb_transport_offset(skb) < nh_min_len) + + transport_offset = skb_transport_offset(skb); + if (transport_offset < nh_min_len || network_offset < 0 || + network_offset > transport_offset - nh_min_len) return -EINVAL; - nh_min_len = skb_transport_offset(skb); + nh_min_len = transport_offset; p_off = nh_min_len + thlen; if (!pskb_may_pull(skb, p_off)) return -EINVAL; @@ -206,9 +255,12 @@ static inline int __virtio_net_hdr_to_skb(struct sk_buff *skb, static inline int virtio_net_hdr_to_skb(struct sk_buff *skb, const struct virtio_net_hdr *hdr, - bool little_endian) + bool little_endian, + int network_offset, + __be16 network_protocol) { - return __virtio_net_hdr_to_skb(skb, hdr, little_endian, hdr->gso_type); + return __virtio_net_hdr_to_skb(skb, hdr, little_endian, hdr->gso_type, + network_offset, network_protocol); } /* This function must be called after virtio_net_hdr_from_skb(). */ @@ -287,7 +339,7 @@ static inline int virtio_net_hdr_from_skb(const struct sk_buff *skb, return 0; } -static inline unsigned int virtio_l3min(bool is_ipv6) +static inline int virtio_l3min(bool is_ipv6) { return is_ipv6 ? sizeof(struct ipv6hdr) : sizeof(struct iphdr); } @@ -297,18 +349,20 @@ virtio_net_hdr_tnl_to_skb(struct sk_buff *skb, const struct virtio_net_hdr_v1_hash_tunnel *vhdr, bool tnl_hdr_negotiated, bool tnl_csum_negotiated, - bool little_endian) + bool little_endian, int network_offset, + __be16 network_protocol) { const struct virtio_net_hdr *hdr = (const struct virtio_net_hdr *)vhdr; - unsigned int inner_nh, outer_th, inner_th; - unsigned int inner_l3min, outer_l3min; u8 gso_inner_type, gso_tunnel_type; bool outer_isv6, inner_isv6; + int inner_nh, outer_th, inner_th; + int inner_l3min, outer_l3min; int ret; gso_tunnel_type = hdr->gso_type & VIRTIO_NET_HDR_GSO_UDP_TUNNEL; if (!gso_tunnel_type) - return virtio_net_hdr_to_skb(skb, hdr, little_endian); + return virtio_net_hdr_to_skb(skb, hdr, little_endian, + network_offset, network_protocol); /* Tunnel not supported/negotiated, but the hdr asks for it. */ if (!tnl_hdr_negotiated) @@ -332,19 +386,24 @@ virtio_net_hdr_tnl_to_skb(struct sk_buff *skb, outer_isv6 = gso_tunnel_type & VIRTIO_NET_HDR_GSO_UDP_TUNNEL_IPV6; inner_isv6 = gso_inner_type == VIRTIO_NET_HDR_GSO_TCPV6; inner_l3min = virtio_l3min(inner_isv6); - outer_l3min = ETH_HLEN + virtio_l3min(outer_isv6); + outer_l3min = virtio_l3min(outer_isv6); + if (network_protocol == htons(ETH_P_IPV6)) + outer_l3min = sizeof(struct ipv6hdr); inner_th = __virtio16_to_cpu(little_endian, hdr->csum_start); inner_nh = le16_to_cpu(vhdr->inner_nh_offset); outer_th = le16_to_cpu(vhdr->outer_th_offset); - if (outer_th < outer_l3min || + if (network_offset < 0 || + outer_th < outer_l3min || + network_offset > outer_th - outer_l3min || inner_nh < outer_th + sizeof(struct udphdr) || inner_th < inner_nh + inner_l3min) return -EINVAL; /* Let the basic parsing deal with plain GSO features. */ ret = __virtio_net_hdr_to_skb(skb, hdr, true, - hdr->gso_type & ~gso_tunnel_type); + hdr->gso_type & ~gso_tunnel_type, + network_offset, network_protocol); if (ret) return ret; diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 50cae32ae..0b37d5474 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2550,6 +2550,26 @@ static void tpacket_destruct_skb(struct sk_buff *skb) sock_wfree(skb); } +static int packet_vnet_hdr_to_skb(struct sk_buff *skb, + const struct virtio_net_hdr *vnet_hdr) +{ + __be16 network_protocol = 0; + int network_offset; + + if (skb->dev->type == ARPHRD_ETHER) { + network_offset = virtio_net_hdr_eth_get_l3_offset(skb, vnet_hdr, + &network_protocol); + } else { + network_offset = skb_network_offset(skb); + network_protocol = skb->protocol; + } + if (network_offset < 0) + return network_offset; + + return virtio_net_hdr_to_skb(skb, vnet_hdr, vio_le(), + network_offset, network_protocol); +} + static int __packet_snd_vnet_parse(struct virtio_net_hdr *vnet_hdr, size_t len) { if ((vnet_hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) && @@ -2901,7 +2921,7 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg) } if (has_vnet_hdr) { - if (virtio_net_hdr_to_skb(skb, &vnet_hdr, vio_le())) { + if (packet_vnet_hdr_to_skb(skb, &vnet_hdr)) { tp_len = -EINVAL; goto tpacket_error; } @@ -3103,7 +3123,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len) packet_parse_headers(skb, sock); if (vnet_hdr_sz) { - err = virtio_net_hdr_to_skb(skb, &vnet_hdr, vio_le()); + err = packet_vnet_hdr_to_skb(skb, &vnet_hdr); if (err) goto out_free; len += vnet_hdr_sz; base-commit: 1e24c4f2ee44be0eee94092b5d13cbdb4bdf0d60 -- 2.46.0