linux-kernel - Re: [RFC][PATCH 2/6] tracing: Fix parsing of globs with a wildcard at the beginning

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Message-Id: <20180208230153.182d38de89e2ce56263cb471@kernel.org>
Date:   Thu, 8 Feb 2018 23:01:53 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...IV.linux.org.uk>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Dmitry Safonov <0x7f454c46@...il.com>, stable@...r.kernel.org
Subject: Re: [RFC][PATCH 2/6] tracing: Fix parsing of globs with a wildcard
 at the beginning

On Tue, 06 Feb 2018 17:43:40 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
> 
> Al Viro reported:
> 
>     For substring - sure, but what about something like "*a*b" and "a*b"?
>     AFAICS, filter_parse_regex() ends up with identical results in both
>     cases - MATCH_GLOB and *search = "a*b".  And no way for the caller
>     to tell one from another.
> 
> Testing this with the following:
> 
>  # cd /sys/kernel/tracing
>  # echo '*raw*lock' > set_ftrace_filter
>  bash: echo: write error: Invalid argument
> 
> With this patch:
> 
>  # echo '*raw*lock' > set_ftrace_filter
>  # cat set_ftrace_filter
> _raw_read_trylock
> _raw_write_trylock
> _raw_read_unlock
> _raw_spin_unlock
> _raw_write_unlock
> _raw_spin_trylock
> _raw_spin_lock
> _raw_write_lock
> _raw_read_lock
> 
> Al recommended not setting the search buffer to skip the first '*' unless we
> know we are not using MATCH_GLOB. This implements his suggested logic.
> 
> Link: http://lkml.kernel.org/r/20180127170748.GF13338@ZenIV.linux.org.uk
> 
> Cc: stable@...r.kernel.org
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Fixes: 60f1d5e3bac44 ("ftrace: Support full glob matching")
> Reported-by: Al Viro <viro@...IV.linux.org.uk>
> Suggsted-by: Al Viro <viro@...IV.linux.org.uk>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

This looks good to me.

Reviewed-by: Masami Hiramatsu <mhiramat@...nel.org>

Thank you!

> ---
>  kernel/trace/trace_events_filter.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
> index 61e7f0678d33..a764aec3c9a1 100644
> --- a/kernel/trace/trace_events_filter.c
> +++ b/kernel/trace/trace_events_filter.c
> @@ -400,7 +400,6 @@ enum regex_type filter_parse_regex(char *buff, int len, char **search, int *not)
>  	for (i = 0; i < len; i++) {
>  		if (buff[i] == '*') {
>  			if (!i) {
> -				*search = buff + 1;
>  				type = MATCH_END_ONLY;
>  			} else if (i == len - 1) {
>  				if (type == MATCH_END_ONLY)
> @@ -410,14 +409,14 @@ enum regex_type filter_parse_regex(char *buff, int len, char **search, int *not)
>  				buff[i] = 0;
>  				break;
>  			} else {	/* pattern continues, use full glob */
> -				type = MATCH_GLOB;
> -				break;
> +				return MATCH_GLOB;
>  			}
>  		} else if (strchr("[?\\", buff[i])) {
> -			type = MATCH_GLOB;
> -			break;
> +			return MATCH_GLOB;
>  		}
>  	}
> +	if (buff[0] == '*')
> +		*search = buff + 1;
>  
>  	return type;
>  }
> -- 
> 2.15.1
> 
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>