linux-kernel - Re: [PATCH v3] tracing/eprobe: no need to check for negative ret value for snprintf

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Date:   Mon, 9 Jan 2023 23:59:13 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Quanfa Fu <quanfafu@...il.com>
Cc:     rostedt@...dmis.org, linux-kernel@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH v3] tracing/eprobe: no need to check for negative ret
 value for snprintf

On Mon,  9 Jan 2023 12:06:25 +0800
Quanfa Fu <quanfafu@...il.com> wrote:

> No need to check for negative return value from snprintf() as the
> code does not return negative values.
> 

Thanks for simplifying, this looks good to me.

Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

> Signed-off-by: Quanfa Fu <quanfafu@...il.com>
> 
> -----
> V2 -> V3: continue to use snprintf
> V1 -> V2: memory allc uses kzalloc and replace snprintf with memcpy
> ---
>  kernel/trace/trace_eprobe.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
> index 352b65e2b910..594ac1d086aa 100644
> --- a/kernel/trace/trace_eprobe.c
> +++ b/kernel/trace/trace_eprobe.c
> @@ -923,17 +923,13 @@ static int trace_eprobe_parse_filter(struct trace_eprobe *ep, int argc, const ch
>  
>  	p = ep->filter_str;
>  	for (i = 0; i < argc; i++) {
> -		ret = snprintf(p, len, "%s ", argv[i]);
> -		if (ret < 0)
> -			goto error;
> -		if (ret > len) {
> -			ret = -E2BIG;
> -			goto error;
> -		}
> +		if (i)
> +			ret = snprintf(p, len, " %s", argv[i]);
> +		else
> +			ret = snprintf(p, len, "%s", argv[i]);
>  		p += ret;
>  		len -= ret;
>  	}
> -	p[-1] = '\0';
>  
>  	/*
>  	 * Ensure the filter string can be parsed correctly. Note, this
> -- 
> 2.31.1
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>