linux-kernel - Re: [PATCH 4/4] tracing/uprobes: Fix the usage of uprobe_buffer_enable() in probe_event

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Date:	Mon, 30 Jun 2014 22:34:09 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Tom Zanussi <tom.zanussi@...ux.intel.com>,
	"zhangwei(Jovi)" <jovi.zhangwei@...wei.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] tracing/uprobes: Fix the usage of
 uprobe_buffer_enable() in probe_event_enable()

> The usage of uprobe_buffer_enable() added by dcad1a20 is very wrong,
> 
> 1. uprobe_buffer_enable() and uprobe_buffer_disable() are not balanced,
>    _enable() should be called only if !enabled.
> 
> 2. If uprobe_buffer_enable() fails probe_event_enable() should clear
>    tp.flags and free event_file_link.
> 
> 3. If uprobe_register() fails it should do uprobe_buffer_disable().
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
(one nit .. )

> +	ret = uprobe_buffer_enable();
> +	if (ret)
> +		goto err_flags;
> +
>  	tu->consumer.filter = filter;
>  	ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
> -	if (ret) {
> -		if (file) {
> -			list_del(&link->list);
> -			kfree(link);
> -			tu->tp.flags &= ~TP_FLAG_TRACE;
> -		} else
> -			tu->tp.flags &= ~TP_FLAG_PROFILE;
> -	}
> +	if (ret)
> +		goto err_buffer;
> 
> +	return 0;
> +
> + err_buffer:
> +	uprobe_buffer_disable();
> +

How about avoiding err_buffer label?
+	if (!ret)
+		return 0;

+	uprobe_buffer_disable();
+


> + err_flags:
> +	if (file) {
> +		list_del(&link->list);
> 
> -- 
> 1.5.5.1
> 

-- 
Thanks and Regards
Srikar Dronamraju

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