Commit a968d5e2 authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Alexei Starovoitov
Browse files

bpf: Move the PTR_TO_BTF_ID check to check_reg_type() 



check_reg_type() checks whether a reg can be used as an arg of a
func_proto.  For PTR_TO_BTF_ID, the check is actually not
completely done until the reg->btf_id is pointing to a
kernel struct that is acceptable by the func_proto.

Thus, this patch moves the btf_id check into check_reg_type().
"arg_type" and "arg_btf_id" are passed to check_reg_type() instead of
"compatible".  The compatible_reg_types[] usage is localized in
check_reg_type() now.

The "if (!btf_id) verbose(...); " is also removed since it won't happen.

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarLorenz Bauer <lmb@cloudflare.com>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200925000344.3854828-1-kafai@fb.com
parent 182bf3f3

kernel/bpf/verifier.c

+31 −29
Original line number Diff line number Diff line
@@ -4028,19 +4028,27 @@ static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = { 
};



static int check_reg_type(struct bpf_verifier_env *env, u32 regno,

			  const struct bpf_reg_types *compatible)

			  enum bpf_arg_type arg_type,

			  const u32 *arg_btf_id)

{

	struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];

	enum bpf_reg_type expected, type = reg->type;

	const struct bpf_reg_types *compatible;

	int i, j;



	compatible = compatible_reg_types[arg_type];

	if (!compatible) {

		verbose(env, "verifier internal error: unsupported arg type %d\n", arg_type);

		return -EFAULT;

	}



	for (i = 0; i < ARRAY_SIZE(compatible->types); i++) {

		expected = compatible->types[i];

		if (expected == NOT_INIT)

			break;



		if (type == expected)

			return 0;

			goto found;

	}



	verbose(env, "R%d type=%s expected=", regno, reg_type_str[type]);
@@ -4048,6 +4056,25 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno, 
		verbose(env, "%s, ", reg_type_str[compatible->types[j]]);

	verbose(env, "%s\n", reg_type_str[compatible->types[j]]);

	return -EACCES;



found:

	if (type == PTR_TO_BTF_ID) {

		if (!btf_struct_ids_match(&env->log, reg->off, reg->btf_id,

					  *arg_btf_id)) {

			verbose(env, "R%d is of type %s but %s is expected\n",

				regno, kernel_type_name(reg->btf_id),

				kernel_type_name(*arg_btf_id));

			return -EACCES;

		}



		if (!tnum_is_const(reg->var_off) || reg->var_off.value) {

			verbose(env, "R%d is a pointer to in-kernel struct with non-zero offset\n",

				regno);

			return -EACCES;

		}

	}



	return 0;

}



static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
@@ -4057,7 +4084,6 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, 
	u32 regno = BPF_REG_1 + arg;

	struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];

	enum bpf_arg_type arg_type = fn->arg_type[arg];

	const struct bpf_reg_types *compatible;

	enum bpf_reg_type type = reg->type;

	int err = 0;
@@ -4097,35 +4123,11 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, 
		 */

		goto skip_type_check;



	compatible = compatible_reg_types[arg_type];

	if (!compatible) {

		verbose(env, "verifier internal error: unsupported arg type %d\n", arg_type);

		return -EFAULT;

	}



	err = check_reg_type(env, regno, compatible);

	err = check_reg_type(env, regno, arg_type, fn->arg_btf_id[arg]);

	if (err)

		return err;



	if (type == PTR_TO_BTF_ID) {

		const u32 *btf_id = fn->arg_btf_id[arg];



		if (!btf_id) {

			verbose(env, "verifier internal error: missing BTF ID\n");

			return -EFAULT;

		}



		if (!btf_struct_ids_match(&env->log, reg->off, reg->btf_id, *btf_id)) {

			verbose(env, "R%d is of type %s but %s is expected\n",

				regno, kernel_type_name(reg->btf_id), kernel_type_name(*btf_id));

			return -EACCES;

		}

		if (!tnum_is_const(reg->var_off) || reg->var_off.value) {

			verbose(env, "R%d is a pointer to in-kernel struct with non-zero offset\n",

				regno);

			return -EACCES;

		}

	} else if (type == PTR_TO_CTX) {

	if (type == PTR_TO_CTX) {

		err = check_ctx_reg(env, reg, regno);

		if (err < 0)

			return err;

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