linux-kernel - Re: [PATCH bpf-next v2 01/28] bpf: add new is_sys_admin_prog

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Message-ID: <CAO-hwJJjDMaTXH9i1UkO7Qy+sbNprDyW67cRp8HryMMWMi5H9w@mail.gmail.com>
Date:   Sat, 5 Mar 2022 11:07:04 +0100
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Song Liu <song@...nel.org>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Jiri Kosina <jikos@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Shuah Khan <shuah@...nel.org>,
        Dave Marchevsky <davemarchevsky@...com>,
        Joe Stringer <joe@...ium.io>,
        Tero Kristo <tero.kristo@...ux.intel.com>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        linux-kselftest@...r.kernel.org, Sean Young <sean@...s.org>
Subject: Re: [PATCH bpf-next v2 01/28] bpf: add new is_sys_admin_prog_type() helper

On Sat, Mar 5, 2022 at 12:12 AM Song Liu <song@...nel.org> wrote:
>
> On Fri, Mar 4, 2022 at 9:30 AM Benjamin Tissoires
> <benjamin.tissoires@...hat.com> wrote:
> >
> > LIRC_MODE2 does not really need net_admin capability, but only sys_admin.
> >
> > Extract a new helper for it, it will be also used for the HID bpf
> > implementation.
> >
> > Cc: Sean Young <sean@...s.org>
> > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
> >
> > ---
> >
> > new in v2
> > ---
> >  kernel/bpf/syscall.c | 14 +++++++++++++-
> >  1 file changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > index db402ebc5570..cc570891322b 100644
> > --- a/kernel/bpf/syscall.c
> > +++ b/kernel/bpf/syscall.c
> > @@ -2165,7 +2165,6 @@ static bool is_net_admin_prog_type(enum bpf_prog_type prog_type)
> >         case BPF_PROG_TYPE_LWT_SEG6LOCAL:
> >         case BPF_PROG_TYPE_SK_SKB:
> >         case BPF_PROG_TYPE_SK_MSG:
> > -       case BPF_PROG_TYPE_LIRC_MODE2:
> >         case BPF_PROG_TYPE_FLOW_DISSECTOR:
> >         case BPF_PROG_TYPE_CGROUP_DEVICE:
> >         case BPF_PROG_TYPE_CGROUP_SOCK:
> > @@ -2202,6 +2201,17 @@ static bool is_perfmon_prog_type(enum bpf_prog_type prog_type)
> >         }
> >  }
> >
> > +static bool is_sys_admin_prog_type(enum bpf_prog_type prog_type)
> > +{
> > +       switch (prog_type) {
> > +       case BPF_PROG_TYPE_LIRC_MODE2:
> > +       case BPF_PROG_TYPE_EXT: /* extends any prog */
> > +               return true;
> > +       default:
> > +               return false;
> > +       }
> > +}
>
> I am not sure whether we should do this. This is a behavior change, that may
> break some user space. Also, BPF_PROG_TYPE_EXT is checked in
> is_perfmon_prog_type(), and this change will make that case useless.

Sure, I can drop it from v3 and make this function appear for HID only.

Regarding BPF_PROG_TYPE_EXT, it was already in both
is_net_admin_prog_type() and is_perfmon_prog_type(), so I duplicated
it here, but I agree, given that it's already in the first function
there, CPA_SYS_ADMIN is already checked.

Cheers,
Benjamin

>
> Thanks,
> Song
>
> [...]
>