From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: bpf@vger.kernel.org, "Alexei Starovoitov" <ast@kernel.org>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Toke Høiland-Jørgensen" <toke@redhat.com>,
"Jesper Dangaard Brouer" <brouer@redhat.com>
Subject: Re: [PATCH bpf-next v2 04/15] bpf: Allow storing referenced kptr in map
Date: Sun, 20 Mar 2022 03:13:03 +0530 [thread overview]
Message-ID: <20220319214303.n3aogzbz3fjaohcy@apollo> (raw)
In-Reply-To: <20220319212320.oos7tao6mybsjt6i@ast-mbp.dhcp.thefacebook.com>
On Sun, Mar 20, 2022 at 02:53:20AM IST, Alexei Starovoitov wrote:
> On Sun, Mar 20, 2022 at 12:29:04AM +0530, Kumar Kartikeya Dwivedi wrote:
> > > >
> > > > if (is_release_function(func_id)) {
> > > > - err = release_reference(env, meta.ref_obj_id);
> > > > + err = -EINVAL;
> > > > + if (meta.ref_obj_id)
> > > > + err = release_reference(env, meta.ref_obj_id);
> > > > + /* Only bpf_kptr_xchg is a release function that accepts a
> > > > + * possibly NULL reg, hence meta.ref_obj_id can only be unset
> > > > + * for it.
> > >
> > > Could you rephrase the comment? I'm not following what it's trying to convey.
> > >
> >
> > All existing release helpers never take a NULL register, so their
> > meta.ref_obj_id will never be unset, but bpf_kptr_xchg can, so it needs some
> > special handling. In check_func_arg, when it jumps to skip_type_check label,
> > reg->ref_obj_id won't be set for NULL value.
>
> I still don't follow.
> What do you mean 'unset meta.ref_obj_id' ?
> It's either set or not.
By unset I meant it is the default (0).
> meta->ref_obj_id will stay zero when arg == NULL.
> Above 'if (meta.ref_obj_id)' makes sense.
> But the code below with extra func_id check looks like defensive programming again.
>
Ok, so I'll just write it like:
if (is_release_function(...) && meta.ref_obj_id) {
err = release_reference(...);
if (err)
...
}
> > > > + */
> > > > + else if (func_id == BPF_FUNC_kptr_xchg)
> > > > + err = 0;
--
Kartikeya
next prev parent reply other threads:[~2022-03-19 21:43 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-17 11:59 [PATCH bpf-next v2 00/15] Introduce typed pointer support in BPF maps Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 01/15] bpf: Factor out fd returning from bpf_btf_find_by_name_kind Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 02/15] bpf: Make btf_find_field more generic Kumar Kartikeya Dwivedi
2022-03-19 17:55 ` Alexei Starovoitov
2022-03-19 19:31 ` Kumar Kartikeya Dwivedi
2022-03-19 20:06 ` Kumar Kartikeya Dwivedi
2022-03-19 21:30 ` Alexei Starovoitov
2022-03-17 11:59 ` [PATCH bpf-next v2 03/15] bpf: Allow storing unreferenced kptr in map Kumar Kartikeya Dwivedi
2022-03-19 18:15 ` Alexei Starovoitov
2022-03-19 18:52 ` Kumar Kartikeya Dwivedi
2022-03-19 21:17 ` Alexei Starovoitov
2022-03-19 21:39 ` Kumar Kartikeya Dwivedi
2022-03-19 21:50 ` Kumar Kartikeya Dwivedi
2022-03-19 22:57 ` Alexei Starovoitov
2022-03-17 11:59 ` [PATCH bpf-next v2 04/15] bpf: Allow storing referenced " Kumar Kartikeya Dwivedi
2022-03-19 18:24 ` Alexei Starovoitov
2022-03-19 18:59 ` Kumar Kartikeya Dwivedi
2022-03-19 21:23 ` Alexei Starovoitov
2022-03-19 21:43 ` Kumar Kartikeya Dwivedi [this message]
2022-03-20 0:57 ` Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 05/15] bpf: Allow storing percpu " Kumar Kartikeya Dwivedi
2022-03-19 18:30 ` Alexei Starovoitov
2022-03-19 19:04 ` Kumar Kartikeya Dwivedi
2022-03-19 21:26 ` Alexei Starovoitov
2022-03-19 21:45 ` Kumar Kartikeya Dwivedi
2022-03-19 23:01 ` Alexei Starovoitov
2022-03-17 11:59 ` [PATCH bpf-next v2 06/15] bpf: Allow storing user " Kumar Kartikeya Dwivedi
2022-03-19 18:28 ` Alexei Starovoitov
2022-03-19 19:02 ` Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 07/15] bpf: Prevent escaping of kptr loaded from maps Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 08/15] bpf: Adapt copy_map_value for multiple offset case Kumar Kartikeya Dwivedi
2022-03-19 18:34 ` Alexei Starovoitov
2022-03-19 19:06 ` Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 09/15] bpf: Always raise reference in btf_get_module_btf Kumar Kartikeya Dwivedi
2022-03-19 18:43 ` Alexei Starovoitov
2022-03-17 11:59 ` [PATCH bpf-next v2 10/15] bpf: Populate pairs of btf_id and destructor kfunc in btf Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 11/15] bpf: Wire up freeing of referenced kptr Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 12/15] bpf: Teach verifier about kptr_get kfunc helpers Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 13/15] libbpf: Add kptr type tag macros to bpf_helpers.h Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 14/15] selftests/bpf: Add C tests for kptr Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 15/15] selftests/bpf: Add verifier " Kumar Kartikeya Dwivedi
2022-03-19 18:50 ` [PATCH bpf-next v2 00/15] Introduce typed pointer support in BPF maps patchwork-bot+netdevbpf
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