linux-kernel - Re: [PATCH 4/4] tracing/filters: Fix MATCH_EBD

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Date:	Fri, 11 Dec 2009 10:14:18 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Wenji Huang <wenji.huang@...cle.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] tracing/filters: Fix MATCH_EBD_ONLY filter matching

On Fri, 2009-12-11 at 17:59 +0800, Li Zefan wrote:
> For '*foo' pattern, we should allow any string ending with
> 'foo', but tracing filter incorrectly disallows strings
> matching regex expression ".*foo.*foo".
> 
> Signed-off-by: Li Zefan <lizf@...fujitsu.com>
> ---
>  kernel/trace/trace_events_filter.c |    5 +++--
>  1 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
> index bd492ce..9f96339 100644
> --- a/kernel/trace/trace_events_filter.c
> +++ b/kernel/trace/trace_events_filter.c
> @@ -276,9 +276,10 @@ static int regex_match_middle(char *str, struct regex *r, int len)
>  
>  static int regex_match_end(char *str, struct regex *r, int len)
>  {
> -	char *ptr = strstr(str, r->pattern);
> +	int strlen = len - 1;
>  
> -	if (ptr && (ptr[r->len] == 0))
> +	if (strlen >= r->len &&
> +	    !memcmp(str + strlen - r->len, r->pattern, r->len))

Please use memcmp() == 0, I've seen too many bugs with !*cmp as well as
with *cmp, because humans tend to think instinctively when reading this
that ! is not a match. With "== 0" we think that "==" is a match and
 "!=" is a miss.

Thanks,


-- Steve

>  		return 1;
>  	return 0;
>  }


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