netdev - Re: [PATCH bpf] tools: bpftool: close prog FD before exit on showing a single program

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Message-ID: <CAEf4BzbL3K5XWSyY6BxrVeF3+3qomsYbXh67yzjyy7ApsosVBw@mail.gmail.com>
Date:   Thu, 15 Aug 2019 10:09:38 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Quentin Monnet <quentin.monnet@...ronome.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        oss-drivers@...ronome.com
Subject: Re: [PATCH bpf] tools: bpftool: close prog FD before exit on showing
 a single program

On Thu, Aug 15, 2019 at 7:24 AM Quentin Monnet
<quentin.monnet@...ronome.com> wrote:
>
> When showing metadata about a single program by invoking
> "bpftool prog show PROG", the file descriptor referring to the program
> is not closed before returning from the function. Let's close it.
>
> Fixes: 71bb428fe2c1 ("tools: bpf: add bpftool")
> Signed-off-by: Quentin Monnet <quentin.monnet@...ronome.com>
> Reviewed-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
> ---
>  tools/bpf/bpftool/prog.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> index 66f04a4846a5..43fdbbfe41bb 100644
> --- a/tools/bpf/bpftool/prog.c
> +++ b/tools/bpf/bpftool/prog.c
> @@ -363,7 +363,9 @@ static int do_show(int argc, char **argv)
>                 if (fd < 0)
>                         return -1;
>
> -               return show_prog(fd);
> +               err = show_prog(fd);
> +               close(fd);
> +               return err;

There is a similar problem few lines above for special case of argc ==
2, which you didn't fix.
Would it be better to make show_prog(fd) close provided fd instead or
is it used in some other context where FD should live longer (I
haven't checked, sorry)?

>         }
>
>         if (argc)
> --
> 2.17.1
>