From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Yonghong Song <yhs@fb.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 09:25:24 -0700 [thread overview]
Message-ID: <20200512162524.4yq4i3or4wtwl43x@ast-mbp> (raw)
In-Reply-To: <c128a30f-af40-99c9-706e-4afe268ed38f@fb.com>
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
> 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.
next prev parent reply other threads:[~2020-05-12 16:25 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 [this message]
2020-05-12 16:29 ` Yonghong Song
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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