linux-kernel - Re: [RFC][PATCH 1/6] ftrace: Remove incorrect setting of glob search field

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Date:   Thu, 8 Feb 2018 23:00:24 +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 1/6] ftrace: Remove incorrect setting of glob
 search field

On Tue, 06 Feb 2018 17:43:39 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
> 
> __unregister_ftrace_function_probe() will incorrectly parse the glob filter
> because it resets the search variable that was setup by filter_parse_regex().
> 
> Al Viro reported this:
> 
>     After that call of filter_parse_regex() we could have func_g.search not
>     equal to glob only if glob started with '!' or '*'.  In the former case
>     we would've buggered off with -EINVAL (not = 1).  In the latter we
>     would've set func_g.search equal to glob + 1, calculated the length of
>     that thing in func_g.len and proceeded to reset func_g.search back to
>     glob.
> 
>     Suppose the glob is e.g. *foo*.  We end up with
> 	    func_g.type = MATCH_MIDDLE_ONLY;
> 	    func_g.len = 3;
> 	    func_g.search = "*foo";
>     Feeding that to ftrace_match_record() will not do anything sane - we
>     will be looking for names containing "*foo" (->len is ignored for that
>     one).
> 
> Link: http://lkml.kernel.org/r/20180127031706.GE13338@ZenIV.linux.org.uk
> 
> Cc: stable@...r.kernel.org
> Cc: Dmitry Safonov <0x7f454c46@...il.com>
> Fixes: 3ba009297149f ("ftrace: Introduce ftrace_glob structure")
> Reported-by: Al Viro <viro@...IV.linux.org.uk>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

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

Thank you!

> ---
>  kernel/trace/ftrace.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index dabd9d167d42..eac9ce2c57a2 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -4456,7 +4456,6 @@ unregister_ftrace_function_probe_func(char *glob, struct trace_array *tr,
>  		func_g.type = filter_parse_regex(glob, strlen(glob),
>  						 &func_g.search, &not);
>  		func_g.len = strlen(func_g.search);
> -		func_g.search = glob;
>  
>  		/* we do not support '!' for function probes */
>  		if (WARN_ON(not))
> -- 
> 2.15.1
> 
> 


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