linux-kernel - Re: [PATCH v1] selftests/bpf: fix application of sizeof to pointer

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Message-ID: <ZzwH77QE/Ch9+evD@pop-os.localdomain>
Date: Mon, 18 Nov 2024 19:37:19 -0800
From: Cong Wang <xiyou.wangcong@...il.com>
To: guanjing <guanjing@...s.chinamobile.com>
Cc: andrii@...nel.org, eddyz87@...il.com, mykolal@...com, ast@...nel.org,
	daniel@...earbox.net, martin.lau@...ux.dev, song@...nel.org,
	yonghong.song@...ux.dev, john.fastabend@...il.com,
	kpsingh@...nel.org, sdf@...ichev.me, haoluo@...gle.com,
	jolsa@...nel.org, shuah@...nel.org, dxu@...uu.xyz,
	antony.antony@...unet.com, cupertino.miranda@...cle.com,
	asavkov@...hat.com, bpf@...r.kernel.org,
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] selftests/bpf: fix application of sizeof to pointer

On Sun, Nov 17, 2024 at 11:18:38AM +0800, guanjing wrote:
> sizeof when applied to a pointer typed expression gives the size of
> the pointer.
> 
> tools/testing/selftests/bpf/progs/test_tunnel_kern.c:678:41-47: ERROR: application of sizeof to pointer
> 
> The proper fix in this particular case is to code sizeof(*gopt)
> instead of sizeof(gopt).
> 
> This issue was detected with the help of Coccinelle.
> 
> Fixes: 5ddafcc377f9 ("selftests/bpf: Fix a few tests for GCC related warnings.")
> Signed-off-by: guanjing <guanjing@...s.chinamobile.com>
> ---
>  tools/testing/selftests/bpf/progs/test_tunnel_kern.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/bpf/progs/test_tunnel_kern.c b/tools/testing/selftests/bpf/progs/test_tunnel_kern.c
> index 32127f1cd687..3a437cdc5c15 100644
> --- a/tools/testing/selftests/bpf/progs/test_tunnel_kern.c
> +++ b/tools/testing/selftests/bpf/progs/test_tunnel_kern.c
> @@ -675,7 +675,7 @@ int ip6geneve_set_tunnel(struct __sk_buff *skb)
>  	gopt->length = 2; /* 4-byte multiple */
>  	*(int *) &gopt->opt_data = bpf_htonl(0xfeedbeef);
>  
> -	ret = bpf_skb_set_tunnel_opt(skb, gopt, sizeof(gopt));
> +	ret = bpf_skb_set_tunnel_opt(skb, gopt, sizeof(*gopt));

Good catch!

I think sizeof(local_gopt) is better, to align with geneve_set_tunnel(),
what do you think?

Thanks.