Re: [PATCH bpf-next v2 01/28] bpf: add new is_sys_admin_prog_type() helper

On Sat, Mar 5, 2022 at 8:58 AM Sean Young [off-list ref] wrote:

On Sat, Mar 05, 2022 at 11:07:04AM +0100, Benjamin Tissoires wrote:

quoted

On Sat, Mar 5, 2022 at 12:12 AM Song Liu [off-list ref] wrote:

quoted

On Fri, Mar 4, 2022 at 9:30 AM Benjamin Tissoires
[off-list ref] wrote:

quoted

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@mess.org>
Signed-off-by: Benjamin Tissoires <redacted>

---

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.

For BPF_PROG_TYPE_LIRC_MODE2, I don't think this change will break userspace.
This is called from ir-keytable(1) which is called from udev. It should have
all the necessary permissions.

In addition, the vast majority IR decoders are non-bpf. bpf ir decoders have
very few users at the moment.

I am working on completely new userspace tooling which will make extensive
use of bpf ir decoding with full lircd and IRP compatibility, but this is not
finished yet (see https://github.com/seanyoung/cir).

Thanks for these information. I guess change for BPF_PROG_TYPE_LIRC_MODE2
is ok then. Would you mind ack or review this change (either current version or
a later version)?

Thanks,
Song