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From: Yonghong Song <yhs@fb.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Andrii Nakryiko <andriin@fb.com>, <bpf@vger.kernel.org>,
	Martin KaFai Lau <kafai@fb.com>, <netdev@vger.kernel.org>,
	Alexei Starovoitov <ast@fb.com>,
	Daniel Borkmann <daniel@iogearbox.net>, <kernel-team@fb.com>
Subject: Re: [PATCH bpf-next v4 02/21] bpf: allow loading of a bpf_iter program
Date: Tue, 12 May 2020 09:29:05 -0700	[thread overview]
Message-ID: <754bce5b-bb4f-69f0-f938-2de3fd4d56ef@fb.com> (raw)
In-Reply-To: <20200512162524.4yq4i3or4wtwl43x@ast-mbp>



On 5/12/20 9:25 AM, Alexei Starovoitov wrote:
> On Tue, May 12, 2020 at 08:41:19AM -0700, Yonghong Song wrote:
>>
>>
>> On 5/9/20 5:41 PM, Alexei Starovoitov wrote:
>>> On Sat, May 09, 2020 at 10:59:00AM -0700, Yonghong Song wrote:
>>>> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
>>>> index 70ad009577f8..d725ff7d11db 100644
>>>> --- a/kernel/bpf/verifier.c
>>>> +++ b/kernel/bpf/verifier.c
>>>> @@ -7101,6 +7101,10 @@ static int check_return_code(struct bpf_verifier_env *env)
>>>>    			return 0;
>>>>    		range = tnum_const(0);
>>>>    		break;
>>>> +	case BPF_PROG_TYPE_TRACING:
>>>> +		if (env->prog->expected_attach_type != BPF_TRACE_ITER)
>>>> +			return 0;
>>>> +		break;
>>>
>>> Not related to this set, but I just noticed that I managed to forget to
>>> add this check for fentry/fexit/freplace.
>>> While it's not too late let's enforce return 0 for them ?
>>> Could you follow up with a patch for bpf tree?
>>
>> Just want to double check. In selftests, we have
>>
>> SEC("fentry/__set_task_comm")
>> int BPF_PROG(prog4, struct task_struct *tsk, const char *buf, bool exec)
>> {
>>          return !tsk;
>> }
>>
>> SEC("fexit/__set_task_comm")
>> int BPF_PROG(prog5, struct task_struct *tsk, const char *buf, bool exec)
>> {
>>          return !tsk;
>> }
>>
>> fentry/fexit may returrn 1. What is the intention here? Does this mean
>> we should allow [0, 1] instead of [0, 0]?
> 
> Argh. I missed that bit when commit ac065870d9282 tweaked the return
> value. For fentry/exit the return value is ignored by trampoline.
> imo it's misleading to users and should be rejected by the verifier.
> so [0,0] for fentry/fexit

Sounds good. Will craft patch to enforce fentry/fexit with [0,0] then.
Thanks!

> 
>> For freplace, we have
>>
>> __u64 test_get_skb_len = 0;
>> SEC("freplace/get_skb_len")
>> int new_get_skb_len(struct __sk_buff *skb)
>> {
>>          int len = skb->len;
>>
>>          if (len != 74)
>>                  return 0;
>>          test_get_skb_len = 1;
>>          return 74; /* original get_skb_len() returns skb->len */
>> }
>>
>> That means freplace may return arbitrary values depending on what
>> to replace?
> 
> yes. freplace and fmod_ret can return anything.
> 

  reply	other threads:[~2020-05-12 16:29 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-09 17:58 [PATCH bpf-next v4 00/21] bpf: implement bpf iterator for kernel data Yonghong Song
2020-05-09 17:58 ` [PATCH bpf-next v4 01/21] bpf: implement an interface to register bpf_iter targets Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 02/21] bpf: allow loading of a bpf_iter program Yonghong Song
2020-05-10  0:41   ` Alexei Starovoitov
2020-05-10  5:07     ` Yonghong Song
2020-05-12 15:41     ` Yonghong Song
2020-05-12 16:25       ` Alexei Starovoitov
2020-05-12 16:29         ` Yonghong Song [this message]
2020-05-09 17:59 ` [PATCH bpf-next v4 03/21] bpf: support bpf tracing/iter programs for BPF_LINK_CREATE Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 04/21] bpf: support bpf tracing/iter programs for BPF_LINK_UPDATE Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 05/21] bpf: implement bpf_seq_read() for bpf iterator Yonghong Song
2020-05-10  0:30   ` Alexei Starovoitov
2020-05-10  4:51     ` Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 06/21] bpf: create anonymous " Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 07/21] bpf: create file " Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 08/21] bpf: implement common macros/helpers for target iterators Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 09/21] bpf: add bpf_map iterator Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 10/21] net: bpf: add netlink and ipv6_route bpf_iter targets Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 11/21] bpf: add task and task/file iterator targets Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 12/21] bpf: add PTR_TO_BTF_ID_OR_NULL support Yonghong Song
2020-05-10  0:50   ` Alexei Starovoitov
2020-05-10  5:18     ` Yonghong Song
2020-05-10 16:11       ` Alexei Starovoitov
2020-05-10 17:05         ` Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 13/21] bpf: add bpf_seq_printf and bpf_seq_write helpers Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 14/21] bpf: handle spilled PTR_TO_BTF_ID properly when checking stack_boundary Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 15/21] bpf: support variable length array in tracing programs Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 16/21] tools/libbpf: add bpf_iter support Yonghong Song
2020-05-10  0:35   ` Alexei Starovoitov
2020-05-10  5:06     ` Yonghong Song
2020-05-10 16:09       ` Alexei Starovoitov
2020-05-10 17:04         ` Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 17/21] tools/libpf: add offsetof/container_of macro in bpf_helpers.h Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 18/21] tools/bpftool: add bpf_iter support for bptool Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 19/21] tools/bpf: selftests: add iterator programs for ipv6_route and netlink Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 20/21] tools/bpf: selftests: add iter progs for bpf_map/task/task_file Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 21/21] tools/bpf: selftests: add bpf_iter selftests Yonghong Song
2020-05-10  0:34   ` Alexei Starovoitov
2020-05-10  5:01     ` Yonghong Song
2020-05-10 16:14       ` Alexei Starovoitov
2020-05-10  0:27 ` [PATCH bpf-next v4 00/21] bpf: implement bpf iterator for kernel data Alexei Starovoitov
2020-05-10  4:47   ` Yonghong Song

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