net/bpf/bpf_dummy_struct_ops.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2021. Huawei Technologies Co., Ltd
   4  */
   5 #include <linux/kernel.h>
   6 #include <linux/bpf_verifier.h>
   7 #include <linux/bpf.h>
   8 #include <linux/btf.h>
   9
  10 static struct bpf_struct_ops bpf_bpf_dummy_ops;
  11
  12 /* A common type for test_N with return value in bpf_dummy_ops */
  13 typedef int (*dummy_ops_test_ret_fn)(struct bpf_dummy_ops_state *state, ...);
  14
  15 static int dummy_ops_test_ret_function(struct bpf_dummy_ops_state *state, ...)
  16 {
  17         return 0;
  18 }
  19
  20 struct bpf_dummy_ops_test_args {
  21         u64 args[MAX_BPF_FUNC_ARGS];
  22         struct bpf_dummy_ops_state state;
  23 };
  24
  25 static struct btf *bpf_dummy_ops_btf;
  26
  27 static struct bpf_dummy_ops_test_args *
  28 dummy_ops_init_args(const union bpf_attr *kattr, unsigned int nr)
  29 {
  30         __u32 size_in;
  31         struct bpf_dummy_ops_test_args *args;
  32         void __user *ctx_in;
  33         void __user *u_state;
  34
  35         size_in = kattr->test.ctx_size_in;
  36         if (size_in != sizeof(u64) * nr)
  37                 return ERR_PTR(-EINVAL);
  38
  39         args = kzalloc(sizeof(*args), GFP_KERNEL);
  40         if (!args)
  41                 return ERR_PTR(-ENOMEM);
  42
  43         ctx_in = u64_to_user_ptr(kattr->test.ctx_in);
  44         if (copy_from_user(args->args, ctx_in, size_in))
  45                 goto out;
  46
  47         /* args[0] is 0 means state argument of test_N will be NULL */
  48         u_state = u64_to_user_ptr(args->args[0]);
  49         if (u_state && copy_from_user(&args->state, u_state,
  50                                       sizeof(args->state)))
  51                 goto out;
  52
  53         return args;
  54 out:
  55         kfree(args);
  56         return ERR_PTR(-EFAULT);
  57 }
  58
  59 static int dummy_ops_copy_args(struct bpf_dummy_ops_test_args *args)
  60 {
  61         void __user *u_state;
  62
  63         u_state = u64_to_user_ptr(args->args[0]);
  64         if (u_state && copy_to_user(u_state, &args->state, sizeof(args->state)))
  65                 return -EFAULT;
  66
  67         return 0;
  68 }
  69
  70 static int dummy_ops_call_op(void *image, struct bpf_dummy_ops_test_args *args)
  71 {
  72         dummy_ops_test_ret_fn test = (void *)image + cfi_get_offset();
  73         struct bpf_dummy_ops_state *state = NULL;
  74
  75         /* state needs to be NULL if args[0] is 0 */
  76         if (args->args[0])
  77                 state = &args->state;
  78         return test(state, args->args[1], args->args[2],
  79                     args->args[3], args->args[4]);
  80 }
  81
  82 static const struct bpf_ctx_arg_aux *find_ctx_arg_info(struct bpf_prog_aux *aux, int offset)
  83 {
  84         int i;
  85
  86         for (i = 0; i < aux->ctx_arg_info_size; i++)
  87                 if (aux->ctx_arg_info[i].offset == offset)
  88                         return &aux->ctx_arg_info[i];
  89
  90         return NULL;
  91 }
  92
  93 /* There is only one check at the moment:
  94  * - zero should not be passed for pointer parameters not marked as nullable.
  95  */
  96 static int check_test_run_args(struct bpf_prog *prog, struct bpf_dummy_ops_test_args *args)
  97 {
  98         const struct btf_type *func_proto = prog->aux->attach_func_proto;
  99
 100         for (u32 arg_no = 0; arg_no < btf_type_vlen(func_proto) ; ++arg_no) {
 101                 const struct btf_param *param = &btf_params(func_proto)[arg_no];
 102                 const struct bpf_ctx_arg_aux *info;
 103                 const struct btf_type *t;
 104                 int offset;
 105
 106                 if (args->args[arg_no] != 0)
 107                         continue;
 108
 109                 /* Program is validated already, so there is no need
 110                  * to check if t is NULL.
 111                  */
 112                 t = btf_type_skip_modifiers(bpf_dummy_ops_btf, param->type, NULL);
 113                 if (!btf_type_is_ptr(t))
 114                         continue;
 115
 116                 offset = btf_ctx_arg_offset(bpf_dummy_ops_btf, func_proto, arg_no);
 117                 info = find_ctx_arg_info(prog->aux, offset);
 118                 if (info && type_may_be_null(info->reg_type))
 119                         continue;
 120
 121                 return -EINVAL;
 122         }
 123
 124         return 0;
 125 }
 126
 127 extern const struct bpf_link_ops bpf_struct_ops_link_lops;
 128
 129 int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,
 130                             union bpf_attr __user *uattr)
 131 {
 132         const struct bpf_struct_ops *st_ops = &bpf_bpf_dummy_ops;
 133         const struct btf_type *func_proto;
 134         struct bpf_dummy_ops_test_args *args;
 135         struct bpf_tramp_links *tlinks = NULL;
 136         struct bpf_tramp_link *link = NULL;
 137         void *image = NULL;
 138         unsigned int op_idx;
 139         u32 image_off = 0;
 140         int prog_ret;
 141         s32 type_id;
 142         int err;
 143
 144         type_id = btf_find_by_name_kind(bpf_dummy_ops_btf,
 145                                         bpf_bpf_dummy_ops.name,
 146                                         BTF_KIND_STRUCT);
 147         if (type_id < 0)
 148                 return -EINVAL;
 149         if (prog->aux->attach_btf_id != type_id)
 150                 return -EOPNOTSUPP;
 151
 152         func_proto = prog->aux->attach_func_proto;
 153         args = dummy_ops_init_args(kattr, btf_type_vlen(func_proto));
 154         if (IS_ERR(args))
 155                 return PTR_ERR(args);
 156
 157         err = check_test_run_args(prog, args);
 158         if (err)
 159                 goto out;
 160
 161         tlinks = kcalloc(BPF_TRAMP_MAX, sizeof(*tlinks), GFP_KERNEL);
 162         if (!tlinks) {
 163                 err = -ENOMEM;
 164                 goto out;
 165         }
 166
 167         link = kzalloc(sizeof(*link), GFP_USER);
 168         if (!link) {
 169                 err = -ENOMEM;
 170                 goto out;
 171         }
 172         /* prog doesn't take the ownership of the reference from caller */
 173         bpf_prog_inc(prog);
 174         bpf_link_init(&link->link, BPF_LINK_TYPE_STRUCT_OPS, &bpf_struct_ops_link_lops, prog);
 175
 176         op_idx = prog->expected_attach_type;
 177         err = bpf_struct_ops_prepare_trampoline(tlinks, link,
 178                                                 &st_ops->func_models[op_idx],
 179                                                 &dummy_ops_test_ret_function,
 180                                                 &image, &image_off,
 181                                                 true);
 182         if (err < 0)
 183                 goto out;
 184
 185         err = arch_protect_bpf_trampoline(image, PAGE_SIZE);
 186         if (err)
 187                 goto out;
 188         prog_ret = dummy_ops_call_op(image, args);
 189
 190         err = dummy_ops_copy_args(args);
 191         if (err)
 192                 goto out;
 193         if (put_user(prog_ret, &uattr->test.retval))
 194                 err = -EFAULT;
 195 out:
 196         kfree(args);
 197         bpf_struct_ops_image_free(image);
 198         if (link)
 199                 bpf_link_put(&link->link);
 200         kfree(tlinks);
 201         return err;
 202 }
 203
 204 static int bpf_dummy_init(struct btf *btf)
 205 {
 206         bpf_dummy_ops_btf = btf;
 207         return 0;
 208 }
 209
 210 static bool bpf_dummy_ops_is_valid_access(int off, int size,
 211                                           enum bpf_access_type type,
 212                                           const struct bpf_prog *prog,
 213                                           struct bpf_insn_access_aux *info)
 214 {
 215         return bpf_tracing_btf_ctx_access(off, size, type, prog, info);
 216 }
 217
 218 static int bpf_dummy_ops_check_member(const struct btf_type *t,
 219                                       const struct btf_member *member,
 220                                       const struct bpf_prog *prog)
 221 {
 222         u32 moff = __btf_member_bit_offset(t, member) / 8;
 223
 224         switch (moff) {
 225         case offsetof(struct bpf_dummy_ops, test_sleepable):
 226                 break;
 227         default:
 228                 if (prog->sleepable)
 229                         return -EINVAL;
 230         }
 231
 232         return 0;
 233 }
 234
 235 static int bpf_dummy_ops_btf_struct_access(struct bpf_verifier_log *log,
 236                                            const struct bpf_reg_state *reg,
 237                                            int off, int size)
 238 {
 239         const struct btf_type *state;
 240         const struct btf_type *t;
 241         s32 type_id;
 242
 243         type_id = btf_find_by_name_kind(reg->btf, "bpf_dummy_ops_state",
 244                                         BTF_KIND_STRUCT);
 245         if (type_id < 0)
 246                 return -EINVAL;
 247
 248         t = btf_type_by_id(reg->btf, reg->btf_id);
 249         state = btf_type_by_id(reg->btf, type_id);
 250         if (t != state) {
 251                 bpf_log(log, "only access to bpf_dummy_ops_state is supported\n");
 252                 return -EACCES;
 253         }
 254
 255         if (off + size > sizeof(struct bpf_dummy_ops_state)) {
 256                 bpf_log(log, "write access at off %d with size %d\n", off, size);
 257                 return -EACCES;
 258         }
 259
 260         return NOT_INIT;
 261 }
 262
 263 static const struct bpf_verifier_ops bpf_dummy_verifier_ops = {
 264         .is_valid_access = bpf_dummy_ops_is_valid_access,
 265         .btf_struct_access = bpf_dummy_ops_btf_struct_access,
 266 };
 267
 268 static int bpf_dummy_init_member(const struct btf_type *t,
 269                                  const struct btf_member *member,
 270                                  void *kdata, const void *udata)
 271 {
 272         return -EOPNOTSUPP;
 273 }
 274
 275 static int bpf_dummy_reg(void *kdata, struct bpf_link *link)
 276 {
 277         return -EOPNOTSUPP;
 278 }
 279
 280 static void bpf_dummy_unreg(void *kdata, struct bpf_link *link)
 281 {
 282 }
 283
 284 static int bpf_dummy_ops__test_1(struct bpf_dummy_ops_state *cb__nullable)
 285 {
 286         return 0;
 287 }
 288
 289 static int bpf_dummy_test_2(struct bpf_dummy_ops_state *cb, int a1, unsigned short a2,
 290                             char a3, unsigned long a4)
 291 {
 292         return 0;
 293 }
 294
 295 static int bpf_dummy_test_sleepable(struct bpf_dummy_ops_state *cb)
 296 {
 297         return 0;
 298 }
 299
 300 static struct bpf_dummy_ops __bpf_bpf_dummy_ops = {
 301         .test_1 = bpf_dummy_ops__test_1,
 302         .test_2 = bpf_dummy_test_2,
 303         .test_sleepable = bpf_dummy_test_sleepable,
 304 };
 305
 306 static struct bpf_struct_ops bpf_bpf_dummy_ops = {
 307         .verifier_ops = &bpf_dummy_verifier_ops,
 308         .init = bpf_dummy_init,
 309         .check_member = bpf_dummy_ops_check_member,
 310         .init_member = bpf_dummy_init_member,
 311         .reg = bpf_dummy_reg,
 312         .unreg = bpf_dummy_unreg,
 313         .name = "bpf_dummy_ops",
 314         .cfi_stubs = &__bpf_bpf_dummy_ops,
 315         .owner = THIS_MODULE,
 316 };
 317
 318 static int __init bpf_dummy_struct_ops_init(void)
 319 {
 320         return register_bpf_struct_ops(&bpf_bpf_dummy_ops, bpf_dummy_ops);
 321 }
 322 late_initcall(bpf_dummy_struct_ops_init);