linux-kernel - Re: [PATCH v2] tracing: fix referencing after memory freeing and refactors code

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Date:	Wed, 6 Nov 2013 14:20:28 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	"Geyslan G. Bem" <geyslan@...il.com>
Cc:	kernel-br@...glegroups.com,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>,
	linux-kernel@...r.kernel.org (open list)
Subject: Re: [PATCH v2] tracing: fix referencing after memory freeing and
 refactors code

On Wed,  6 Nov 2013 16:02:51 -0300
"Geyslan G. Bem" <geyslan@...il.com> wrote:

> In 'system_tr_open()':
> Fix possible 'dir' assignment after freeing it.

I'll take this patch, but I'm going to reword the subject and the
change log. The assignment of dir to filp->private_data after dir is
freed is not as bad as it sounds. As we are returning an error,
filp->private_data is never used.

-- Steve


> 
> In both functions:
> Restructures logic conditions testing 'tracing_is_disabled()'
> return before the others tests.
> 
> Signed-off-by: Geyslan G. Bem <geyslan@...il.com>
> ---
>  kernel/trace/trace_events.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 368a4d5..b44a7ea 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -1062,6 +1062,9 @@ static int subsystem_open(struct inode *inode, struct file *filp)
>  	struct trace_array *tr;
>  	int ret;
>  
> +	if (tracing_is_disabled())
> +		return -ENODEV;
> +
>  	/* Make sure the system still exists */
>  	mutex_lock(&trace_types_lock);
>  	mutex_lock(&event_mutex);
> @@ -1108,6 +1111,9 @@ static int system_tr_open(struct inode *inode, struct file *filp)
>  	struct trace_array *tr = inode->i_private;
>  	int ret;
>  
> +	if (tracing_is_disabled())
> +		return -ENODEV;
> +
>  	if (trace_array_get(tr) < 0)
>  		return -ENODEV;
>  
> @@ -1124,11 +1130,12 @@ static int system_tr_open(struct inode *inode, struct file *filp)
>  	if (ret < 0) {
>  		trace_array_put(tr);
>  		kfree(dir);
> +		return ret;
>  	}
>  
>  	filp->private_data = dir;
>  
> -	return ret;
> +	return 0;
>  }
>  
>  static int subsystem_release(struct inode *inode, struct file *file)

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