linux-kernel - Re: [PATCH] tracing: Fix double free of event_trigger

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Date:   Thu, 26 Jul 2018 07:51:29 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Hiraku Toyooka <hiraku.toyooka@...ertrust.co.jp>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] tracing: Fix double free of event_trigger_data

On Wed, 25 Jul 2018 15:53:21 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Wed, 25 Jul 2018 15:29:04 -0400
> Steven Rostedt <rostedt@...dmis.org> wrote:
> 
> > Nope, this doesn't work. It's a little more complex than the other one.
> > I'll just leave it, and fix the reg code for 4.19.
> 
> I take this back. Looks like it just needs to be handled slightly
> differently. Thoughts?

Ah, I see, the filter should be cleared :)
OK, this should work.

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

Thanks,

> 
> -- Steve
> 
> diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
> index d18ec0e58be2..5dea177cef53 100644
> --- a/kernel/trace/trace_events_trigger.c
> +++ b/kernel/trace/trace_events_trigger.c
> @@ -1420,6 +1420,9 @@ int event_enable_trigger_func(struct event_command *cmd_ops,
>  		goto out;
>  	}
>  
> +	/* Up the trigger_data count to make sure nothing frees it on failure */
> +	event_trigger_init(trigger_ops, trigger_data);
> +
>  	if (trigger) {
>  		number = strsep(&trigger, ":");
>  
> @@ -1470,6 +1473,7 @@ int event_enable_trigger_func(struct event_command *cmd_ops,
>  		goto out_disable;
>  	/* Just return zero, not the number of enabled functions */
>  	ret = 0;
> +	event_trigger_free(trigger_ops, trigger_data);
>   out:
>  	return ret;
>  
> @@ -1480,7 +1484,7 @@ int event_enable_trigger_func(struct event_command *cmd_ops,
>   out_free:
>  	if (cmd_ops->set_filter)
>  		cmd_ops->set_filter(NULL, trigger_data, NULL);
> -	kfree(trigger_data);
> +	event_trigger_free(trigger_ops, trigger_data);
>  	kfree(enable_data);
>  	goto out;
>  }


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