linux-kernel - Re: [PATCH] tracing: Don't use the address of the buffer array name in copy_from

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Date:	Tue, 26 Apr 2016 12:37:11 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Wang Xiaoqiang <wangxq10@....edu.cn>
Cc:	Chunyu Hu <chuhu@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Jiaxing Wang <hello.wjx@...il.com>,
	Chen Gang <gang.chen.5i5j@...il.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Joe Perches <joe@...ches.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing: Don't use the address of the buffer array name
 in copy_from_user

On Mon, 18 Apr 2016 15:23:29 +0800
Wang Xiaoqiang <wangxq10@....edu.cn> wrote:

> Hi, all,
> 
> From 7dbacb179a4d5f9ac9d7e1b3733664b3b0fe23ae Mon Sep 17 00:00:00 2001
> From: Wang Xiaoqiang <wangxq10@....edu.cn>
> Date: Mon, 18 Apr 2016 14:58:15 +0800
> Subject: [PATCH] tracing: Don't use the address of the buffer array name in
>  copy_from_user
> 
> Fix the problem as follows:

What problem is being fixed?

> 
>     ...
>     char buf[64];
>     ...
>     if (copy_from_user(&buf, ubuf, cnt))
>     ...
> 
> Even though the value of "&buf" equals "buf", but there is no need
> to get the address of the "buf" again. Use "buf" replace "&buf".

I'll take this, but more as a cleanup and not a "fix".

Thanks,

-- Steve

> 
> Signed-off-by: Wang Xiaoqiang <wangxq10@....edu.cn>
> ---
>  kernel/trace/trace.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index a2f0b9f..422ab57 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -3658,7 +3658,7 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf,
>  	if (cnt >= sizeof(buf))
>  		return -EINVAL;
>  
> -	if (copy_from_user(&buf, ubuf, cnt))
> +	if (copy_from_user(buf, ubuf, cnt))
>  		return -EFAULT;
>  
>  	buf[cnt] = 0;
> @@ -4474,7 +4474,7 @@ tracing_set_trace_write(struct file *filp, const char __user *ubuf,
>  	if (cnt > MAX_TRACER_SIZE)
>  		cnt = MAX_TRACER_SIZE;
>  
> -	if (copy_from_user(&buf, ubuf, cnt))
> +	if (copy_from_user(buf, ubuf, cnt))
>  		return -EFAULT;
>  
>  	buf[cnt] = 0;
> @@ -5264,7 +5264,7 @@ static ssize_t tracing_clock_write(struct file *filp, const char __user *ubuf,
>  	if (cnt >= sizeof(buf))
>  		return -EINVAL;
>  
> -	if (copy_from_user(&buf, ubuf, cnt))
> +	if (copy_from_user(buf, ubuf, cnt))
>  		return -EFAULT;
>  
>  	buf[cnt] = 0;