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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Yonghong Song <yhs@fb.com>
Cc: bpf@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
	Cong Wang <xiyou.wangcong@gmail.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	kernel-team@fb.com
Subject: Re: [PATCH bpf-next v2 04/11] bpf: add bpf_for_each_map_elem() helper
Date: Mon, 22 Feb 2021 12:59:12 -0800	[thread overview]
Message-ID: <20210222205912.hucaxodzk7csrdyj@ast-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <20210217181807.3190187-1-yhs@fb.com>

On Wed, Feb 17, 2021 at 10:18:07AM -0800, Yonghong Song wrote:
> @@ -5893,6 +6004,14 @@ static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg,
>  		else
>  			*ptr_limit = -off;
>  		return 0;
> +	case PTR_TO_MAP_KEY:
> +		if (mask_to_left) {
> +			*ptr_limit = ptr_reg->umax_value + ptr_reg->off;
> +		} else {
> +			off = ptr_reg->smin_value + ptr_reg->off;
> +			*ptr_limit = ptr_reg->map_ptr->key_size - off;
> +		}
> +		return 0;

This part cannot be exercised because for_each will require cap_bpf.
Eventually we might relax this requirement and above code will be necessary.
Could you manually test it that it's working as expected by forcing
sanitize_ptr_alu() to act on it?

>  	case PTR_TO_MAP_VALUE:
>  		if (mask_to_left) {
>  			*ptr_limit = ptr_reg->umax_value + ptr_reg->off;
> @@ -6094,6 +6213,7 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
>  		verbose(env, "R%d pointer arithmetic on %s prohibited\n",
>  			dst, reg_type_str[ptr_reg->type]);
>  		return -EACCES;
> +	case PTR_TO_MAP_KEY:
>  	case PTR_TO_MAP_VALUE:
>  		if (!env->allow_ptr_leaks && !known && (smin_val < 0) != (smax_val < 0)) {
>  			verbose(env, "R%d has unknown scalar with mixed signed bounds, pointer arithmetic with it prohibited for !root\n",
> @@ -8273,6 +8393,21 @@ static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
>  		return 0;
>  	}
>  
> +	if (insn->src_reg == BPF_PSEUDO_FUNC) {
> +		struct bpf_prog_aux *aux = env->prog->aux;
> +		u32 subprogno = insn[1].imm;
> +
> +		if (aux->func_info &&
> +		    aux->func_info_aux[subprogno].linkage != BTF_FUNC_STATIC) {

Could you change above to "!aux->func_info || aux..." ?
That will force for_each to be available only when funcs are annotated.
The subprogs without annotations were added only to be able to manually
craft asm test cases for subprogs in test_verifier.
The for_each selftests in patches 10 and 11 are strong enough.
The asm test would not add any value.
So I would like to avoid supporting something that has no real use.

  reply	other threads:[~2021-02-22 21:00 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-17 18:18 [PATCH bpf-next v2 00/11] bpf: add bpf_for_each_map_elem() helper Yonghong Song
2021-02-17 18:18 ` [PATCH bpf-next v2 01/11] bpf: factor out visit_func_call_insn() in check_cfg() Yonghong Song
2021-02-17 18:18 ` [PATCH bpf-next v2 02/11] bpf: factor out verbose_invalid_scalar() Yonghong Song
2021-02-17 18:18 ` [PATCH bpf-next v2 03/11] bpf: refactor check_func_call() to allow callback function Yonghong Song
2021-02-17 18:18 ` [PATCH bpf-next v2 04/11] bpf: add bpf_for_each_map_elem() helper Yonghong Song
2021-02-22 20:59   ` Alexei Starovoitov [this message]
2021-02-23 18:39     ` Yonghong Song
2021-02-23 18:46       ` Alexei Starovoitov
2021-02-23 19:37         ` Yonghong Song
2021-02-17 18:18 ` [PATCH bpf-next v2 05/11] bpf: add hashtab support for " Yonghong Song
2021-02-22 22:56   ` Alexei Starovoitov
2021-02-23 18:41     ` Yonghong Song
2021-02-17 18:18 ` [PATCH bpf-next v2 06/11] bpf: add arraymap " Yonghong Song
2021-02-17 18:18 ` [PATCH bpf-next v2 07/11] libbpf: move function is_ldimm64() earlier in libbpf.c Yonghong Song
2021-02-23  8:06   ` Andrii Nakryiko
2021-02-17 18:18 ` [PATCH bpf-next v2 08/11] libbpf: support local function pointer relocation Yonghong Song
2021-02-23  8:03   ` Andrii Nakryiko
2021-02-23 18:55     ` Yonghong Song
2021-02-23 19:07       ` Alexei Starovoitov
2021-02-23 19:21         ` Andrii Nakryiko
2021-02-23 19:19       ` Andrii Nakryiko
2021-02-23 19:47         ` Yonghong Song
2021-02-23 21:24           ` Andrii Nakryiko
2021-02-17 18:18 ` [PATCH bpf-next v2 09/11] bpftool: print local function pointer properly Yonghong Song
2021-02-23  8:06   ` Andrii Nakryiko
2021-02-23 19:00     ` Yonghong Song
2021-02-17 18:18 ` [PATCH bpf-next v2 10/11] selftests/bpf: add hashmap test for bpf_for_each_map_elem() helper Yonghong Song
2021-02-17 18:18 ` [PATCH bpf-next v2 11/11] selftests/bpf: add arraymap " Yonghong Song
2021-02-17 18:29 ` [PATCH bpf-next v2 00/11] bpf: add " Yonghong Song

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