netdev - Re: [PATCH v2 bpf-next 01/16] bpf: Introduce bpf_sys

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Message-ID: <CAEf4BzY5BrSOWj8zc+hBd5jm_p4OaH7gzR5voEwOwvQFPvBcPw@mail.gmail.com>
Date:   Mon, 26 Apr 2021 09:51:30 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH v2 bpf-next 01/16] bpf: Introduce bpf_sys_bpf() helper and
 program type.

On Thu, Apr 22, 2021 at 5:26 PM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> From: Alexei Starovoitov <ast@...nel.org>
>
> Add placeholders for bpf_sys_bpf() helper and new program type.
>
> v1->v2:
> - check that expected_attach_type is zero
> - allow more helper functions to be used in this program type, since they will
>   only execute from user context via bpf_prog_test_run.
>
> Signed-off-by: Alexei Starovoitov <ast@...nel.org>
> ---

LGTM, see minor comments below.

Acked-by: Andrii Nakryiko <andrii@...nel.org>

>  include/linux/bpf.h            | 10 +++++++
>  include/linux/bpf_types.h      |  2 ++
>  include/uapi/linux/bpf.h       |  8 +++++
>  kernel/bpf/syscall.c           | 54 ++++++++++++++++++++++++++++++++++
>  net/bpf/test_run.c             | 43 +++++++++++++++++++++++++++
>  tools/include/uapi/linux/bpf.h |  8 +++++
>  6 files changed, 125 insertions(+)
>

[...]

> +
> +const struct bpf_func_proto * __weak
> +tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> +{
> +

extra empty line

> +       return bpf_base_func_proto(func_id);
> +}
> +
> +static const struct bpf_func_proto *
> +syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> +{
> +       switch (func_id) {
> +       case BPF_FUNC_sys_bpf:
> +               return &bpf_sys_bpf_proto;
> +       default:
> +               return tracing_prog_func_proto(func_id, prog);
> +       }
> +}
> +

[...]

> +       if (ctx_size_in) {
> +               ctx = kzalloc(ctx_size_in, GFP_USER);
> +               if (!ctx)
> +                       return -ENOMEM;
> +               if (copy_from_user(ctx, ctx_in, ctx_size_in)) {
> +                       err = -EFAULT;
> +                       goto out;
> +               }
> +       }
> +       retval = bpf_prog_run_pin_on_cpu(prog, ctx);
> +
> +       if (copy_to_user(&uattr->test.retval, &retval, sizeof(u32)))
> +               err = -EFAULT;

is there a point in trying to do another copy_to_user if this fails?
I.e., why not goto out here?

> +       if (ctx_size_in)
> +               if (copy_to_user(ctx_in, ctx, ctx_size_in)) {
> +                       err = -EFAULT;
> +                       goto out;
> +               }
> +out:
> +       kfree(ctx);
> +       return err;
> +}

[...]