linux-kernel - Re: [PATCH v3 bpf] tools: bpftool: Add missing close before bpftool net attach exit

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Date:   Wed, 11 Nov 2020 22:24:12 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Wang Hai <wanghai38@...wei.com>, john.fastabend@...il.com,
        quentin@...valent.com, mrostecki@...nsuse.org
Cc:     ast@...nel.org, kafai@...com, songliubraving@...com, yhs@...com,
        andrii@...nel.org, kpsingh@...omium.org, toke@...hat.com,
        danieltimlee@...il.com, bpf@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 bpf] tools: bpftool: Add missing close before bpftool
 net attach exit

On 11/11/20 2:54 PM, Wang Hai wrote:
> progfd is created by prog_parse_fd(), before 'bpftool net attach' exit,
> it should be closed.
> 
> Fixes: 04949ccc273e ("tools: bpftool: add net attach command to attach XDP on interface")
> Signed-off-by: Wang Hai <wanghai38@...wei.com>
> ---
> v2->v3: add 'err = 0' before successful return
> v1->v2: use cleanup tag instead of repeated closes
>   tools/bpf/bpftool/net.c | 18 +++++++++++-------
>   1 file changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/tools/bpf/bpftool/net.c b/tools/bpf/bpftool/net.c
> index 910e7bac6e9e..f927392271cc 100644
> --- a/tools/bpf/bpftool/net.c
> +++ b/tools/bpf/bpftool/net.c
> @@ -578,8 +578,8 @@ static int do_attach(int argc, char **argv)
>   
>   	ifindex = net_parse_dev(&argc, &argv);
>   	if (ifindex < 1) {
> -		close(progfd);
> -		return -EINVAL;
> +		err = -EINVAL;
> +		goto cleanup;
>   	}
>   
>   	if (argc) {
> @@ -587,8 +587,8 @@ static int do_attach(int argc, char **argv)
>   			overwrite = true;
>   		} else {
>   			p_err("expected 'overwrite', got: '%s'?", *argv);
> -			close(progfd);
> -			return -EINVAL;
> +			err = -EINVAL;
> +			goto cleanup;
>   		}
>   	}
>   
> @@ -597,16 +597,20 @@ static int do_attach(int argc, char **argv)
>   		err = do_attach_detach_xdp(progfd, attach_type, ifindex,
>   					   overwrite);
>   
> -	if (err < 0) {
> +	if (err) {
>   		p_err("interface %s attach failed: %s",
>   		      attach_type_strings[attach_type], strerror(-err));
> -		return err;
> +		goto cleanup;
>   	}
>   
>   	if (json_output)
>   		jsonw_null(json_wtr);
>   
> -	return 0;
> +	err = 0;

Why is the 'err = 0' still needed here given we test for err != 0 earlier?
Would just remove it, otherwise looks good.

> +cleanup:
> +	close(progfd);
> +	return err;
>   }
>   
>   static int do_detach(int argc, char **argv)
>