Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 | // SPDX-License-Identifier: GPL-2.0-only /* Copyright (c) 2017 Facebook */ #include <stddef.h> #include <string.h> #include <linux/bpf.h> #include <linux/if_ether.h> #include <linux/if_packet.h> #include <linux/ip.h> #include <linux/ipv6.h> #include <linux/in.h> #include <linux/tcp.h> #include <linux/pkt_cls.h> #include <bpf/bpf_helpers.h> #include <bpf/bpf_endian.h> #define barrier() __asm__ __volatile__("": : :"memory") int _version SEC("version") = 1; /* llvm will optimize both subprograms into exactly the same BPF assembly * * Disassembly of section .text: * * 0000000000000000 test_pkt_access_subprog1: * ; return skb->len * 2; * 0: 61 10 00 00 00 00 00 00 r0 = *(u32 *)(r1 + 0) * 1: 64 00 00 00 01 00 00 00 w0 <<= 1 * 2: 95 00 00 00 00 00 00 00 exit * * 0000000000000018 test_pkt_access_subprog2: * ; return skb->len * val; * 3: 61 10 00 00 00 00 00 00 r0 = *(u32 *)(r1 + 0) * 4: 64 00 00 00 01 00 00 00 w0 <<= 1 * 5: 95 00 00 00 00 00 00 00 exit * * Which makes it an interesting test for BTF-enabled verifier. */ static __attribute__ ((noinline)) int test_pkt_access_subprog1(volatile struct __sk_buff *skb) { return skb->len * 2; } static __attribute__ ((noinline)) int test_pkt_access_subprog2(int val, volatile struct __sk_buff *skb) { return skb->len * val; } #define MAX_STACK (512 - 2 * 32) __attribute__ ((noinline)) int get_skb_len(struct __sk_buff *skb) { volatile char buf[MAX_STACK] = {}; return skb->len; } __attribute__ ((noinline)) int get_constant(long val) { return val - 122; } int get_skb_ifindex(int, struct __sk_buff *skb, int); __attribute__ ((noinline)) int test_pkt_access_subprog3(int val, struct __sk_buff *skb) { return get_skb_len(skb) * get_skb_ifindex(val, skb, get_constant(123)); } __attribute__ ((noinline)) int get_skb_ifindex(int val, struct __sk_buff *skb, int var) { volatile char buf[MAX_STACK] = {}; return skb->ifindex * val * var; } __attribute__ ((noinline)) int test_pkt_write_access_subprog(struct __sk_buff *skb, __u32 off) { void *data = (void *)(long)skb->data; void *data_end = (void *)(long)skb->data_end; struct tcphdr *tcp = NULL; if (off > sizeof(struct ethhdr) + sizeof(struct ipv6hdr)) return -1; tcp = data + off; if (tcp + 1 > data_end) return -1; /* make modification to the packet data */ tcp->check++; return 0; } SEC("classifier/test_pkt_access") int test_pkt_access(struct __sk_buff *skb) { void *data_end = (void *)(long)skb->data_end; void *data = (void *)(long)skb->data; struct ethhdr *eth = (struct ethhdr *)(data); struct tcphdr *tcp = NULL; __u8 proto = 255; __u64 ihl_len; if (eth + 1 > data_end) return TC_ACT_SHOT; if (eth->h_proto == bpf_htons(ETH_P_IP)) { struct iphdr *iph = (struct iphdr *)(eth + 1); if (iph + 1 > data_end) return TC_ACT_SHOT; ihl_len = iph->ihl * 4; proto = iph->protocol; tcp = (struct tcphdr *)((void *)(iph) + ihl_len); } else if (eth->h_proto == bpf_htons(ETH_P_IPV6)) { struct ipv6hdr *ip6h = (struct ipv6hdr *)(eth + 1); if (ip6h + 1 > data_end) return TC_ACT_SHOT; ihl_len = sizeof(*ip6h); proto = ip6h->nexthdr; tcp = (struct tcphdr *)((void *)(ip6h) + ihl_len); } if (test_pkt_access_subprog1(skb) != skb->len * 2) return TC_ACT_SHOT; if (test_pkt_access_subprog2(2, skb) != skb->len * 2) return TC_ACT_SHOT; if (test_pkt_access_subprog3(3, skb) != skb->len * 3 * skb->ifindex) return TC_ACT_SHOT; if (tcp) { if (test_pkt_write_access_subprog(skb, (void *)tcp - data)) return TC_ACT_SHOT; if (((void *)(tcp) + 20) > data_end || proto != 6) return TC_ACT_SHOT; barrier(); /* to force ordering of checks */ if (((void *)(tcp) + 18) > data_end) return TC_ACT_SHOT; if (tcp->urg_ptr == 123) return TC_ACT_OK; } return TC_ACT_UNSPEC; } |