Commit d7b9454a authored by Lorenz Bauer's avatar Lorenz Bauer Committed by Alexei Starovoitov
Browse files

bpf: Make BTF pointer type checking generic 



Perform BTF type checks if the register we're working on contains a BTF
pointer, rather than if the argument is for a BTF pointer. This is easier
to understand, and allows removing the code from the arg_type checking
section of the function.

Signed-off-by: default avatarLorenz Bauer <lmb@cloudflare.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200921121227.255763-6-lmb@cloudflare.com
parent 9436ef6e

kernel/bpf/verifier.c

+20 −18
Original line number Diff line number Diff line
@@ -4048,27 +4048,9 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, 
				goto err_type;

		}

	} else if (arg_type == ARG_PTR_TO_BTF_ID) {

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



		expected_type = PTR_TO_BTF_ID;

		if (type != expected_type)

			goto err_type;



		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 (arg_type == ARG_PTR_TO_SPIN_LOCK) {

		if (meta->func_id == BPF_FUNC_spin_lock) {

			if (process_spin_lock(env, regno, true))
@@ -4123,6 +4105,26 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, 
		return -EFAULT;

	}



	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;

		}

	}



	if (arg_type == ARG_CONST_MAP_PTR) {

		/* bpf_map_xxx(map_ptr) call: remember that map_ptr */

		meta->map_ptr = reg->map_ptr;