Re: [PATCH bpf-next v2 1/5] bpf: Allow helper bpf_get_[ns_]current_pid_tgid() for all prog types

[Jiri Olsa <olsajiri@gmail.com>]

On Fri, Mar 15, 2024 at 11:48:54AM -0700, Yonghong Song wrote:
> Currently bpf_get_current_pid_tgid() is allowed in tracing, cgroup
> and sk_msg progs while bpf_get_ns_current_pid_tgid() is only allowed
> in tracing progs.
> 
> We have an internal use case where for an application running
> in a container (with pid namespace), user wants to get
> the pid associated with the pid namespace in a cgroup bpf
> program. Currently, cgroup bpf progs already allow
> bpf_get_current_pid_tgid(). Let us allow bpf_get_ns_current_pid_tgid()
> as well.
> 
> With auditing the code, bpf_get_current_pid_tgid() is also used
> by sk_msg prog. But there are no side effect to expose these two
> helpers to all prog types since they do not reveal any kernel specific
> data. The detailed discussion is in [1].
> 
> So with this patch, both bpf_get_current_pid_tgid() and bpf_get_ns_current_pid_tgid()
> are put in bpf_base_func_proto(), making them available to all
> program types.
> 
>   [1] https://lore.kernel.org/bpf/20240307232659.1115872-1-yonghong.song@linux.dev/
> 
> Signed-off-by: Yonghong Song <yonghong.song@linux.dev>

Acked-by: Jiri Olsa <jolsa@kernel.org>

jirka

> ---
>  kernel/bpf/cgroup.c      | 2 --
>  kernel/bpf/helpers.c     | 4 ++++
>  kernel/trace/bpf_trace.c | 4 ----
>  net/core/filter.c        | 2 --
>  4 files changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
> index 82243cb6c54d..8ba73042a239 100644
> --- a/kernel/bpf/cgroup.c
> +++ b/kernel/bpf/cgroup.c
> @@ -2575,8 +2575,6 @@ cgroup_current_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>  	switch (func_id) {
>  	case BPF_FUNC_get_current_uid_gid:
>  		return &bpf_get_current_uid_gid_proto;
> -	case BPF_FUNC_get_current_pid_tgid:
> -		return &bpf_get_current_pid_tgid_proto;
>  	case BPF_FUNC_get_current_comm:
>  		return &bpf_get_current_comm_proto;
>  #ifdef CONFIG_CGROUP_NET_CLASSID
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index a89587859571..9234174ccb21 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -1730,6 +1730,10 @@ bpf_base_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>  		return &bpf_strtol_proto;
>  	case BPF_FUNC_strtoul:
>  		return &bpf_strtoul_proto;
> +	case BPF_FUNC_get_current_pid_tgid:
> +		return &bpf_get_current_pid_tgid_proto;
> +	case BPF_FUNC_get_ns_current_pid_tgid:
> +		return &bpf_get_ns_current_pid_tgid_proto;
>  	default:
>  		break;
>  	}
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 0a5c4efc73c3..1b041911b1d8 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -1525,8 +1525,6 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>  		return &bpf_ktime_get_boot_ns_proto;
>  	case BPF_FUNC_tail_call:
>  		return &bpf_tail_call_proto;
> -	case BPF_FUNC_get_current_pid_tgid:
> -		return &bpf_get_current_pid_tgid_proto;
>  	case BPF_FUNC_get_current_task:
>  		return &bpf_get_current_task_proto;
>  	case BPF_FUNC_get_current_task_btf:
> @@ -1582,8 +1580,6 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>  		return &bpf_send_signal_thread_proto;
>  	case BPF_FUNC_perf_event_read_value:
>  		return &bpf_perf_event_read_value_proto;
> -	case BPF_FUNC_get_ns_current_pid_tgid:
> -		return &bpf_get_ns_current_pid_tgid_proto;
>  	case BPF_FUNC_ringbuf_output:
>  		return &bpf_ringbuf_output_proto;
>  	case BPF_FUNC_ringbuf_reserve:
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 8adf95765cdd..0c66e4a3fc5b 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -8342,8 +8342,6 @@ sk_msg_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>  		return &bpf_event_output_data_proto;
>  	case BPF_FUNC_get_current_uid_gid:
>  		return &bpf_get_current_uid_gid_proto;
> -	case BPF_FUNC_get_current_pid_tgid:
> -		return &bpf_get_current_pid_tgid_proto;
>  	case BPF_FUNC_sk_storage_get:
>  		return &bpf_sk_storage_get_proto;
>  	case BPF_FUNC_sk_storage_delete:
> -- 
> 2.43.0
> 
>