Re: [PATCH ftrace/core 3/3] trace: Fix memory leak when new instance creation failed

[Steven Rostedt]

On Fri, 06 Jun 2014 07:35:22 +0900
Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@xxxxxxxxxxx> wrote:

> Current new_instance_create() implements just two fail paths for four
> allocation operations. So, it can induce memory leak if new instance
> creation failed. This patch fixes it by defining all fail paths and
> freeing allocated memories appropriately.
> 
> Signed-off-by: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@xxxxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> ---
>  kernel/trace/trace.c |   23 ++++++++++++++---------
>  1 file changed, 14 insertions(+), 9 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 473eb68..bbd86d2 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -6277,7 +6277,7 @@ static int new_instance_create(const char *name)
>  		goto out_free_tr;
>  
>  	if (!alloc_cpumask_var(&tr->tracing_cpumask, GFP_KERNEL))
> -		goto out_free_tr;
> +		goto out_free_tr_name;
>  
>  	cpumask_copy(tr->tracing_cpumask, cpu_all_mask);
>  
> @@ -6291,16 +6291,16 @@ static int new_instance_create(const char *name)
>  	INIT_LIST_HEAD(&tr->events);
>  
>  	if (allocate_trace_buffers(tr, trace_buf_size) < 0)
> -		goto out_free_tr;
> +		goto out_free_cpumask_var;
>  
>  	tr->dir = debugfs_create_dir(name, trace_instance_dir);
>  	if (!tr->dir)
> -		goto out_free_tr;
> +		goto out_free_trace_buffers;
>  
>  	ret = event_trace_add_tracer(tr->dir, tr);
>  	if (ret) {
>  		debugfs_remove_recursive(tr->dir);
> -		goto out_free_tr;
> +		goto out_free_trace_buffers;
>  	}
>  
>  	init_tracer_debugfs(tr, tr->dir);
> @@ -6311,18 +6311,23 @@ static int new_instance_create(const char *name)
>  
>  	return 0;
>  
> - out_free_tr:
> -	if (tr->trace_buffer.buffer)
> -		ring_buffer_free(tr->trace_buffer.buffer);
> + out_free_trace_buffers:
> +	ring_buffer_free(tr->trace_buffer.buffer);
> +	free_percpu(tr->trace_buffer.data);
> +#ifdef CONFIG_TRACER_MAX_TRACE
> +	ring_buffer_free(tr->max_buffer.buffer);
> +	free_percpu(tr->max_buffer.data);
> +#endif

I think we need a free_trace_buffer() that complements
allocate_trace_buffer().

-- Steve

> + out_free_cpumask_var:
>  	free_cpumask_var(tr->tracing_cpumask);
> + out_free_tr_name:
>  	kfree(tr->name);
> + out_free_tr:
>  	kfree(tr);
> -
>   out_unlock:
>  	mutex_unlock(&trace_types_lock);
>  
>  	return ret;
> -
>  }
>  
>  static int instance_delete(const char *name)

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