net/netfilter/xt_bpf.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Xtables module to match packets using a BPF filter.
   3  * Copyright 2013 Google Inc.
   4  * Written by Willem de Bruijn <willemb@google.com>
   5  */
   6
   7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   8
   9 #include <linux/module.h>
  10 #include <linux/syscalls.h>
  11 #include <linux/skbuff.h>
  12 #include <linux/filter.h>
  13 #include <linux/bpf.h>
  14
  15 #include <linux/netfilter/xt_bpf.h>
  16 #include <linux/netfilter/x_tables.h>
  17
  18 MODULE_AUTHOR("Willem de Bruijn <willemb@google.com>");
  19 MODULE_DESCRIPTION("Xtables: BPF filter match");
  20 MODULE_LICENSE("GPL");
  21 MODULE_ALIAS("ipt_bpf");
  22 MODULE_ALIAS("ip6t_bpf");
  23
  24 static int __bpf_mt_check_bytecode(struct sock_filter *insns, __u16 len,
  25                                    struct bpf_prog **ret)
  26 {
  27         struct sock_fprog_kern program;
  28
  29         if (len > XT_BPF_MAX_NUM_INSTR)
  30                 return -EINVAL;
  31
  32         program.len = len;
  33         program.filter = insns;
  34
  35         if (bpf_prog_create(ret, &program)) {
  36                 pr_info_ratelimited("check failed: parse error\n");
  37                 return -EINVAL;
  38         }
  39
  40         return 0;
  41 }
  42
  43 static int __bpf_mt_check_fd(int fd, struct bpf_prog **ret)
  44 {
  45         struct bpf_prog *prog;
  46
  47         prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SOCKET_FILTER);
  48         if (IS_ERR(prog))
  49                 return PTR_ERR(prog);
  50
  51         *ret = prog;
  52         return 0;
  53 }
  54
  55 static int __bpf_mt_check_path(const char *path, struct bpf_prog **ret)
  56 {
  57         if (strnlen(path, XT_BPF_PATH_MAX) == XT_BPF_PATH_MAX)
  58                 return -EINVAL;
  59
  60         *ret = bpf_prog_get_type_path(path, BPF_PROG_TYPE_SOCKET_FILTER);
  61         return PTR_ERR_OR_ZERO(*ret);
  62 }
  63
  64 static int bpf_mt_check(const struct xt_mtchk_param *par)
  65 {
  66         struct xt_bpf_info *info = par->matchinfo;
  67
  68         return __bpf_mt_check_bytecode(info->bpf_program,
  69                                        info->bpf_program_num_elem,
  70                                        &info->filter);
  71 }
  72
  73 static int bpf_mt_check_v1(const struct xt_mtchk_param *par)
  74 {
  75         struct xt_bpf_info_v1 *info = par->matchinfo;
  76
  77         if (info->mode == XT_BPF_MODE_BYTECODE)
  78                 return __bpf_mt_check_bytecode(info->bpf_program,
  79                                                info->bpf_program_num_elem,
  80                                                &info->filter);
  81         else if (info->mode == XT_BPF_MODE_FD_ELF)
  82                 return __bpf_mt_check_fd(info->fd, &info->filter);
  83         else if (info->mode == XT_BPF_MODE_PATH_PINNED)
  84                 return __bpf_mt_check_path(info->path, &info->filter);
  85         else
  86                 return -EINVAL;
  87 }
  88
  89 static bool bpf_mt(const struct sk_buff *skb, struct xt_action_param *par)
  90 {
  91         const struct xt_bpf_info *info = par->matchinfo;
  92
  93         return BPF_PROG_RUN(info->filter, skb);
  94 }
  95
  96 static bool bpf_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
  97 {
  98         const struct xt_bpf_info_v1 *info = par->matchinfo;
  99
 100         return !!bpf_prog_run_save_cb(info->filter, (struct sk_buff *) skb);
 101 }
 102
 103 static void bpf_mt_destroy(const struct xt_mtdtor_param *par)
 104 {
 105         const struct xt_bpf_info *info = par->matchinfo;
 106
 107         bpf_prog_destroy(info->filter);
 108 }
 109
 110 static void bpf_mt_destroy_v1(const struct xt_mtdtor_param *par)
 111 {
 112         const struct xt_bpf_info_v1 *info = par->matchinfo;
 113
 114         bpf_prog_destroy(info->filter);
 115 }
 116
 117 static struct xt_match bpf_mt_reg[] __read_mostly = {
 118         {
 119                 .name           = "bpf",
 120                 .revision       = 0,
 121                 .family         = NFPROTO_UNSPEC,
 122                 .checkentry     = bpf_mt_check,
 123                 .match          = bpf_mt,
 124                 .destroy        = bpf_mt_destroy,
 125                 .matchsize      = sizeof(struct xt_bpf_info),
 126                 .usersize       = offsetof(struct xt_bpf_info, filter),
 127                 .me             = THIS_MODULE,
 128         },
 129         {
 130                 .name           = "bpf",
 131                 .revision       = 1,
 132                 .family         = NFPROTO_UNSPEC,
 133                 .checkentry     = bpf_mt_check_v1,
 134                 .match          = bpf_mt_v1,
 135                 .destroy        = bpf_mt_destroy_v1,
 136                 .matchsize      = sizeof(struct xt_bpf_info_v1),
 137                 .usersize       = offsetof(struct xt_bpf_info_v1, filter),
 138                 .me             = THIS_MODULE,
 139         },
 140 };
 141
 142 static int __init bpf_mt_init(void)
 143 {
 144         return xt_register_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
 145 }
 146
 147 static void __exit bpf_mt_exit(void)
 148 {
 149         xt_unregister_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
 150 }
 151
 152 module_init(bpf_mt_init);
 153 module_exit(bpf_mt_exit);