net/netfilter/xt_bpf.c

   1 /* Xtables module to match packets using a BPF filter.
   2  * Copyright 2013 Google Inc.
   3  * Written by Willem de Bruijn <willemb@google.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/syscalls.h>
  12 #include <linux/skbuff.h>
  13 #include <linux/filter.h>
  14 #include <linux/bpf.h>
  15
  16 #include <linux/netfilter/xt_bpf.h>
  17 #include <linux/netfilter/x_tables.h>
  18
  19 MODULE_AUTHOR("Willem de Bruijn <willemb@google.com>");
  20 MODULE_DESCRIPTION("Xtables: BPF filter match");
  21 MODULE_LICENSE("GPL");
  22 MODULE_ALIAS("ipt_bpf");
  23 MODULE_ALIAS("ip6t_bpf");
  24
  25 static int __bpf_mt_check_bytecode(struct sock_filter *insns, __u16 len,
  26                                    struct bpf_prog **ret)
  27 {
  28         struct sock_fprog_kern program;
  29
  30         if (len > XT_BPF_MAX_NUM_INSTR)
  31                 return -EINVAL;
  32
  33         program.len = len;
  34         program.filter = insns;
  35
  36         if (bpf_prog_create(ret, &program)) {
  37                 pr_info("bpf: check failed: parse error\n");
  38                 return -EINVAL;
  39         }
  40
  41         return 0;
  42 }
  43
  44 static int __bpf_mt_check_fd(int fd, struct bpf_prog **ret)
  45 {
  46         struct bpf_prog *prog;
  47
  48         prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SOCKET_FILTER);
  49         if (IS_ERR(prog))
  50                 return PTR_ERR(prog);
  51
  52         *ret = prog;
  53         return 0;
  54 }
  55
  56 static int __bpf_mt_check_path(const char *path, struct bpf_prog **ret)
  57 {
  58         mm_segment_t oldfs = get_fs();
  59         int retval, fd;
  60
  61         if (strnlen(path, XT_BPF_PATH_MAX) == XT_BPF_PATH_MAX)
  62                 return -EINVAL;
  63
  64         set_fs(KERNEL_DS);
  65         fd = bpf_obj_get_user(path);
  66         set_fs(oldfs);
  67         if (fd < 0)
  68                 return fd;
  69
  70         retval = __bpf_mt_check_fd(fd, ret);
  71         sys_close(fd);
  72         return retval;
  73 }
  74
  75 static int bpf_mt_check(const struct xt_mtchk_param *par)
  76 {
  77         struct xt_bpf_info *info = par->matchinfo;
  78
  79         return __bpf_mt_check_bytecode(info->bpf_program,
  80                                        info->bpf_program_num_elem,
  81                                        &info->filter);
  82 }
  83
  84 static int bpf_mt_check_v1(const struct xt_mtchk_param *par)
  85 {
  86         struct xt_bpf_info_v1 *info = par->matchinfo;
  87
  88         if (info->mode == XT_BPF_MODE_BYTECODE)
  89                 return __bpf_mt_check_bytecode(info->bpf_program,
  90                                                info->bpf_program_num_elem,
  91                                                &info->filter);
  92         else if (info->mode == XT_BPF_MODE_FD_ELF)
  93                 return __bpf_mt_check_fd(info->fd, &info->filter);
  94         else if (info->mode == XT_BPF_MODE_PATH_PINNED)
  95                 return __bpf_mt_check_path(info->path, &info->filter);
  96         else
  97                 return -EINVAL;
  98 }
  99
 100 static bool bpf_mt(const struct sk_buff *skb, struct xt_action_param *par)
 101 {
 102         const struct xt_bpf_info *info = par->matchinfo;
 103
 104         return BPF_PROG_RUN(info->filter, skb);
 105 }
 106
 107 static bool bpf_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
 108 {
 109         const struct xt_bpf_info_v1 *info = par->matchinfo;
 110
 111         return !!bpf_prog_run_save_cb(info->filter, (struct sk_buff *) skb);
 112 }
 113
 114 static void bpf_mt_destroy(const struct xt_mtdtor_param *par)
 115 {
 116         const struct xt_bpf_info *info = par->matchinfo;
 117
 118         bpf_prog_destroy(info->filter);
 119 }
 120
 121 static void bpf_mt_destroy_v1(const struct xt_mtdtor_param *par)
 122 {
 123         const struct xt_bpf_info_v1 *info = par->matchinfo;
 124
 125         bpf_prog_destroy(info->filter);
 126 }
 127
 128 static struct xt_match bpf_mt_reg[] __read_mostly = {
 129         {
 130                 .name           = "bpf",
 131                 .revision       = 0,
 132                 .family         = NFPROTO_UNSPEC,
 133                 .checkentry     = bpf_mt_check,
 134                 .match          = bpf_mt,
 135                 .destroy        = bpf_mt_destroy,
 136                 .matchsize      = sizeof(struct xt_bpf_info),
 137                 .usersize       = offsetof(struct xt_bpf_info, filter),
 138                 .me             = THIS_MODULE,
 139         },
 140         {
 141                 .name           = "bpf",
 142                 .revision       = 1,
 143                 .family         = NFPROTO_UNSPEC,
 144                 .checkentry     = bpf_mt_check_v1,
 145                 .match          = bpf_mt_v1,
 146                 .destroy        = bpf_mt_destroy_v1,
 147                 .matchsize      = sizeof(struct xt_bpf_info_v1),
 148                 .usersize       = offsetof(struct xt_bpf_info_v1, filter),
 149                 .me             = THIS_MODULE,
 150         },
 151 };
 152
 153 static int __init bpf_mt_init(void)
 154 {
 155         return xt_register_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
 156 }
 157
 158 static void __exit bpf_mt_exit(void)
 159 {
 160         xt_unregister_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
 161 }
 162
 163 module_init(bpf_mt_init);
 164 module_exit(bpf_mt_exit);