linux-kernel - Re: [PATCH bpf-next 2/2] bpftool: Check argc first before "file" in do

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Date:   Mon, 14 Nov 2022 09:30:17 -0800
From:   sdf@...gle.com
To:     Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc:     Quentin Monnet <quentin@...valent.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next 2/2] bpftool: Check argc first before "file" in do_batch()

On 11/14, Tiezhu Yang wrote:
> If the parameters for batch are more than 2, check argc first can
> return immediately, no need to use strcmp() to check "file" with
> a little overhead and then check argc, it is better to check "file"
> only when the parameters for batch are 2.

Seems fine if you respin with is_prefix instead of strcmp.
Has the potential of breaking some buggy users which pass
more than one file, but I don't think it's a good justification
no to do the fix? Quentin?


> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
> ---
>   tools/bpf/bpftool/main.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)

> diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
> index 4ef87c2..27d6dbf 100644
> --- a/tools/bpf/bpftool/main.c
> +++ b/tools/bpf/bpftool/main.c
> @@ -337,12 +337,12 @@ static int do_batch(int argc, char **argv)
>   	if (argc < 2) {
>   		p_err("too few parameters for batch");
>   		return -1;
> -	} else if (strcmp(*argv, "file")) {
> -		p_err("expected 'file', got: %s", *argv);
> -		return -1;
>   	} else if (argc > 2) {
>   		p_err("too many parameters for batch");
>   		return -1;
> +	} else if (strcmp(*argv, "file")) {
> +		p_err("expected 'file', got: %s", *argv);
> +		return -1;
>   	}
>   	NEXT_ARG();

> --
> 2.1.0