diff --git a/net/netfilter/nft_payload.c b/net/netfilter/nft_payload.c index 345eff140d56..9c974df59b42 100644 --- a/net/netfilter/nft_payload.c +++ b/net/netfilter/nft_payload.c @@ -834,6 +834,172 @@ nft_payload_set_vlan(const u32 *src, struct sk_buff *skb, u16 offset, u8 len, return true; } +/* Ingress is very early, before l3 protocol handlers. + * There should be no in-tree code that trusts l3/l4 headers + * between ingress and NF_INET_PRE_ROUTING hooks. + */ +static bool nft_in_ingress(const struct nf_hook_state *s) +{ + return s->pf == NFPROTO_NETDEV && s->hook == NF_NETDEV_INGRESS; +} + +static bool nft_nh_write_ok_ip4(const struct nft_pktinfo *pkt, + const struct nft_payload_set *priv, + const u32 *src) +{ + unsigned int offset = priv->offset + skb_network_offset(pkt->skb); + const u8 *new_octets = (const u8 *)src; + u8 old_octet; + + switch (priv->offset) { + case 0: /* csum fixups does expand dscp/tos store to 2 bytes. + * make sure ihl/version remain unchanged. + */ + if (skb_copy_bits(pkt->skb, offset, &old_octet, sizeof(old_octet))) + return false; + + return priv->len == 2 && + *new_octets == old_octet; + case offsetof(struct iphdr, tos): + return priv->len == 1; + case offsetof(struct iphdr, id): + return priv->len == 2; + case offsetof(struct iphdr, ttl): + if (priv->len == 1) + return true; + + if (priv->len != 2) + return false; + + /* same, csum fixup does expand ttl store to two bytes. + * check protocol is not altered. + */ + if (skb_copy_bits(pkt->skb, offset + 1, &old_octet, sizeof(old_octet))) + return false; + + return new_octets[1] == old_octet; + case offsetof(struct iphdr, check): + return priv->len <= 2 + 4 + 4; + case offsetof(struct iphdr, saddr): + return priv->len <= 4 + 4; + case offsetof(struct iphdr, daddr): + return priv->len <= 4; + } + + return false; +} + +static bool nft_nh_write_ok_ip6(const struct nft_pktinfo *pkt, + const struct nft_payload_set *priv, + const u32 *src) +{ + const struct ipv6hdr *ih = (const void *)src; + + switch (priv->offset) { + case 0: /* store to dscp must not alter ip6 version */ + return priv->len <= 4 && ih->version == 6; + case 2: + return priv->len <= 2; + case offsetof(struct ipv6hdr, hop_limit): + return priv->len == 1; + case offsetof(struct ipv6hdr, saddr): + return priv->len <= 16 + 16; + case offsetof(struct ipv6hdr, daddr): + return priv->len <= 16; + } + + return false; +} + +static bool nft_nh_write_ok_arp(const struct nft_payload_set *priv) +{ + /* Variable size for standard ethernet arp */ + const unsigned int eth_ip = 2 * (ETH_ALEN + 4); + unsigned int offset = priv->offset; + + switch (offset) { + case offsetof(struct arphdr, ar_op): + return priv->len == 2; + default: + break; + } + + /* permit writes post fixed arp header size. offset + len are + * checked vs skb size via skb_ensure_writable. + */ + return offset >= sizeof(struct arphdr) && priv->len <= eth_ip; +} + +static bool nft_nh_write_ok_netdev(const struct nft_pktinfo *pkt, + const struct nft_payload_set *priv, + const u32 *src) +{ +#ifdef CONFIG_NF_TABLES_NETDEV + switch (pkt->skb->protocol) { + case htons(ETH_P_ARP): + return nft_nh_write_ok_arp(priv); + case htons(ETH_P_IP): + return nft_nh_write_ok_ip4(pkt, priv, src); + case htons(ETH_P_IPV6): + return nft_nh_write_ok_ip6(pkt, priv, src); + } +#endif + /* default to false for now, relax later in case we have + * use-cases that need inner header manipulation for + * encapsulated traffic like vlan or PPPoE. + */ + return false; +} + +static bool nft_nh_write_ok_bridge(const struct nft_pktinfo *pkt, + const struct nft_payload_set *priv, + const u32 *src) +{ +#if IS_ENABLED(CONFIG_NF_TABLES_BRIDGE) + switch (pkt->ethertype) { + case htons(ETH_P_ARP): + return nft_nh_write_ok_arp(priv); + case htons(ETH_P_IP): + return nft_nh_write_ok_ip4(pkt, priv, src); + case htons(ETH_P_IPV6): + return nft_nh_write_ok_ip6(pkt, priv, src); + } +#endif + /* see nft_nh_write_ok_netdev: default to false */ + return false; +} + +static bool nft_nh_write_ok(const struct nft_pktinfo *pkt, + const struct nft_payload_set *priv, + const u32 *src) +{ + switch (pkt->state->pf) { + case NFPROTO_ARP: + return nft_nh_write_ok_arp(priv); + case NFPROTO_BRIDGE: + return nft_nh_write_ok_bridge(pkt, priv, src); + case NFPROTO_IPV4: + return nft_nh_write_ok_ip4(pkt, priv, src); + case NFPROTO_IPV6: + return nft_nh_write_ok_ip6(pkt, priv, src); + case NFPROTO_NETDEV: + if (pkt->state->hook == NF_NETDEV_INGRESS) + return true; + return nft_nh_write_ok_netdev(pkt, priv, src); + } + + return false; +} + +/* check linklayer modifications don't spill into network header. */ +static bool nft_ll_write_ok(const struct nft_pktinfo *pkt, int offset) +{ + if (nft_in_ingress(pkt->state)) + return true; + + return offset <= skb_network_offset(pkt->skb); +} + static void nft_payload_set_eval(const struct nft_expr *expr, struct nft_regs *regs, const struct nft_pktinfo *pkt) @@ -861,8 +1027,12 @@ static void nft_payload_set_eval(const struct nft_expr *expr, } offset = skb_mac_header(skb) - skb->data - vlan_hlen; + if (!nft_ll_write_ok(pkt, priv->len + priv->offset + offset)) + goto err; break; case NFT_PAYLOAD_NETWORK_HEADER: + if (!nft_nh_write_ok(pkt, priv, src)) + goto err; offset = skb_network_offset(skb); break; case NFT_PAYLOAD_TRANSPORT_HEADER: