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Message-ID: <6ac9f767-e7f5-6603-6234-97126ea22005@iogearbox.net>
Date: Mon, 5 Dec 2022 22:10:56 +0100
From: Daniel Borkmann <daniel@...earbox.net>
To: Xin Liu <liuxin350@...wei.com>, andrii@...nel.org, ast@...nel.org,
martin.lau@...ux.dev, song@...nel.org, yhs@...com,
john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
haoluo@...gle.com, jolsa@...nel.org
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
yanan@...wei.com, wuchangye@...wei.com, xiesongyang@...wei.com,
kongweibin2@...wei.com, zhangmingyi5@...wei.com
Subject: Re: [PATCH bpf-next] libbpf: Optimized return value in
libbpf_strerror when errno is libbpf errno
On 12/3/22 10:37 AM, Xin Liu wrote:
> This is a small improvement in libbpf_strerror. When libbpf_strerror
> is used to obtain the system error description, if the length of the
> buf is insufficient, libbpf_sterror returns ERANGE and sets errno to
> ERANGE.
>
> However, this processing is not performed when the error code
> customized by libbpf is obtained. Make some minor improvements here,
> return -ERANGE and set errno to ERANGE when buf is not enough for
> custom description.
>
> Signed-off-by: Xin Liu <liuxin350@...wei.com>
> ---
> tools/lib/bpf/libbpf_errno.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf_errno.c b/tools/lib/bpf/libbpf_errno.c
> index 96f67a772a1b..48ce7d5b5bf9 100644
> --- a/tools/lib/bpf/libbpf_errno.c
> +++ b/tools/lib/bpf/libbpf_errno.c
> @@ -54,10 +54,16 @@ int libbpf_strerror(int err, char *buf, size_t size)
>
> if (err < __LIBBPF_ERRNO__END) {
> const char *msg;
> + size_t msg_size;
>
> msg = libbpf_strerror_table[ERRNO_OFFSET(err)];
> snprintf(buf, size, "%s", msg);
> buf[size - 1] = '\0';
> +
> + msg_size = strlen(msg);
> + if (msg_size >= size)
> + return libbpf_err(-ERANGE);
Given this is related to libbpf_strerror_table[] where the error strings are known
lets do compile-time error instead. All callers should pass in a buffer of STRERR_BUFSIZE
size in libbpf.
> return 0;
> }
>
>
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