linux-kernel - Re: [PATCH] libbpf: Initialize st

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Message-ID: <66d4df96-3493-4b12-8bd8-e26c42cd342d@wanadoo.fr>
Date: Wed, 21 Aug 2024 09:20:04 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Soma Nakata <soma.nakata01@...il.com>, Alexei Starovoitov
 <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau
 <martin.lau@...ux.dev>, Eduard Zingerman <eddyz87@...il.com>,
 Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] libbpf: Initialize st_ops->tname with strdup()

Le 21/08/2024 à 08:46, Soma Nakata a écrit :
> `tname` is returned by `btf__name_by_offset()` as well as `var_name`,
> and these addresses point to strings in the btf. Since their locations
> may change while loading the bpf program, using `strdup()` ensures
> `tname` is safely stored.
> 
> Signed-off-by: Soma Nakata <soma.nakata01@...il.com>
> ---
>   tools/lib/bpf/libbpf.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index a3be6f8fac09..ece1f1af2cd4 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -1423,7 +1423,7 @@ static int init_struct_ops_maps(struct bpf_object *obj, const char *sec_name,
>   		memcpy(st_ops->data,
>   		       data->d_buf + vsi->offset,
>   		       type->size);
> -		st_ops->tname = tname;
> +		st_ops->tname = strdup(tname);

Hi,

Should a NULL check be added (as done a few lines above for the 
[cm]alloc()) and bpf_map__destroy() updated with a 
zfree(&map->st_ops->tname) ?

CJ

>   		st_ops->type = type;
>   		st_ops->type_id = type_id;
>