linux-kernel - Re: [RFC PATCH 2/5] kprobes: Use helper to parse boolean input from userspace

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Date:   Wed, 9 Jun 2021 23:37:59 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Punit Agrawal <punitagrawal@...il.com>
Cc:     naveen.n.rao@...ux.ibm.com, anil.s.keshavamurthy@...el.com,
        davem@...emloft.net, linux-kernel@...r.kernel.org,
        guoren@...nel.org, linux-csky@...r.kernel.org
Subject: Re: [RFC PATCH 2/5] kprobes: Use helper to parse boolean input from
 userspace

On Wed,  9 Jun 2021 19:50:16 +0900
Punit Agrawal <punitagrawal@...il.com> wrote:

> The "enabled" file provides a debugfs interface to arm / disarm
> kprobes in the kernel. In order to parse the buffer containing the
> values written from userspace, the callback manually parses the user
> input to convert it to a boolean value.
> 
> As taking a string value from userspace and converting it to boolean
> is a common operation, a helper kstrtobool_from_user() is already
> available in the kernel. Update the callback to use the common helper
> to parse the write buffer from userspace.

Looks good to me.

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

Thank you!

> 
> Signed-off-by: Punit Agrawal <punitagrawal@...il.com>
> ---
>  kernel/kprobes.c | 28 ++++++----------------------
>  1 file changed, 6 insertions(+), 22 deletions(-)
> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index fdb1ea2e963b..1a11d3c411bf 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -2777,30 +2777,14 @@ static ssize_t read_enabled_file_bool(struct file *file,
>  static ssize_t write_enabled_file_bool(struct file *file,
>  	       const char __user *user_buf, size_t count, loff_t *ppos)
>  {
> -	char buf[32];
> -	size_t buf_size;
> -	int ret = 0;
> -
> -	buf_size = min(count, (sizeof(buf)-1));
> -	if (copy_from_user(buf, user_buf, buf_size))
> -		return -EFAULT;
> +	bool enable;
> +	int ret;
>  
> -	buf[buf_size] = '\0';
> -	switch (buf[0]) {
> -	case 'y':
> -	case 'Y':
> -	case '1':
> -		ret = arm_all_kprobes();
> -		break;
> -	case 'n':
> -	case 'N':
> -	case '0':
> -		ret = disarm_all_kprobes();
> -		break;
> -	default:
> -		return -EINVAL;
> -	}
> +	ret = kstrtobool_from_user(user_buf, count, &enable);
> +	if (ret)
> +		return ret;
>  
> +	ret = enable ? arm_all_kprobes() : disarm_all_kprobes();
>  	if (ret)
>  		return ret;
>  
> -- 
> 2.30.2
> 


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