linux-kernel - Re: [PATCH] libbpf: check the btf

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Message-ID: <ZrIH1_UYOYWkaawc@krava>
Date: Tue, 6 Aug 2024 13:24:07 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Ma Ke <make24@...as.ac.cn>
Cc: andrii@...nel.org, eddyz87@...il.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,
	delyank@...com, bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] libbpf: check the btf_type kind to prevent error

On Tue, Aug 06, 2024 at 06:51:42PM +0800, Ma Ke wrote:
> To prevent potential error return values, it is necessary to check the
> return value of btf__type_by_id. We can add a kind checking to fix the
> issue.
> 
> Cc: stable@...r.kernel.org
> Fixes: 430025e5dca5 ("libbpf: Add subskeleton scaffolding")
> Signed-off-by: Ma Ke <make24@...as.ac.cn>
> ---
>  tools/lib/bpf/libbpf.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index a3be6f8fac09..d1eb45d16054 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -13850,6 +13850,9 @@ int bpf_object__open_subskeleton(struct bpf_object_subskeleton *s)
>  		var = btf_var_secinfos(map_type);
>  		for (i = 0; i < len; i++, var++) {
>  			var_type = btf__type_by_id(btf, var->type);
> +			if (!var_type)
> +				return libbpf_err(-ENOENT);

hum btf__type_by_id sets errno to EINVAL in case of error

I think we should keep that or just pass errno like we do earlier in the function

  libbpf_err(-errno)

jirka

> +
>  			var_name = btf__name_by_offset(btf, var_type->name_off);
>  			if (strcmp(var_name, var_skel->name) == 0) {
>  				*var_skel->addr = map->mmaped + var->offset;
> -- 
> 2.25.1
>