linux-kernel - Re: [PATCH v2] lib: parser: optimize match

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Message-ID: <Y75gI7HRTiNzdfM4@sol.localdomain>
Date:   Tue, 10 Jan 2023 23:07:15 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Li Lingfeng <lilingfeng3@...wei.com>
Cc:     linux-kernel@...r.kernel.org, tj@...nel.org,
        akpm@...ux-foundation.org, jack@...e.cz, bingjingc@...ology.com,
        james.smart@...adcom.com, houtao1@...wei.com, yi.zhang@...wei.com,
        yangerkun@...wei.com, yukuai3@...wei.com
Subject: Re: [PATCH v2] lib: parser: optimize match_NUMER apis to use local
 array

On Wed, Jan 11, 2023 at 12:22:15PM +0800, Li Lingfeng wrote:
>  /**
>   * match_one - Determines if a string matches a simple pattern
>   * @s: the string to examine for presence of the pattern
> @@ -129,14 +138,13 @@ EXPORT_SYMBOL(match_token);
>  static int match_number(substring_t *s, int *result, int base)
>  {
>  	char *endp;
> -	char *buf;
> +	char buf[NUMBER_BUF_LEN];
>  	int ret;
>  	long val;
>  
> -	buf = match_strdup(s);
> -	if (!buf)
> -		return -ENOMEM;
> -
> +	if ((s->to - s->from) >= NUMBER_BUF_LEN)
> +		return -ERANGE;
> +	match_strlcpy(buf, s, NUMBER_BUF_LEN);

Instead of doing '(s->to - s->from) >= NUMBER_BUF_LEN', it would be simpler to
check the return value of match_strlcpy():

	if (match_strlcpy(buf, s, NUMBER_BUF_LEN) >= NUMBER_BUF_LEN)
		return -ERANGE;

Likewise in match_u64int() and match_uint().

- Eric