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(). The compatible_reg_types[] usage is localized in check_reg_type() now which I found it easier to reason in the next patch. The "if (!btf_id) verbose(...); " is removed for now since it won't happen. It will be added back in the next patch with new error log specific to mis-configured compatible_reg_types[]. Signed-off-by: Martin KaFai Lau <kafai@xxxxxx> --- kernel/bpf/verifier.c | 65 +++++++++++++++++++++++-------------------- 1 file changed, 35 insertions(+), 30 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 8fdef5656e7f..3a5932bd7c22 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3981,20 +3981,29 @@ static const struct bpf_reg_types *compatible_reg_types[] = { [__BPF_ARG_TYPE_MAX] = NULL, }; -static int check_reg_type(struct bpf_verifier_env *env, u32 regno, - const struct bpf_reg_types *compatible) +static int check_reg_type(struct bpf_verifier_env *env, u32 arg, + enum bpf_arg_type arg_type, + const struct bpf_func_proto *fn) { + u32 regno = BPF_REG_1 + arg; struct bpf_reg_state *regs = cur_regs(env), *reg = ®s[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]); @@ -4002,6 +4011,27 @@ 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) { + u32 *expected_btf_id = fn->arg_btf_id[arg]; + + if (!btf_struct_ids_match(&env->log, reg->off, reg->btf_id, + *expected_btf_id)) { + verbose(env, "R%d is a pointer to in-kernel struct %s but %s is expected instead\n", + regno, kernel_type_name(reg->btf_id), + kernel_type_name(*expected_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, @@ -4011,7 +4041,6 @@ 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 = ®s[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; @@ -4051,35 +4080,11 @@ 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, arg, arg_type, fn); 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 has incompatible type %s\n", regno, - kernel_type_name(reg->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; -- 2.24.1