linux-kernel - Re: [PATCH] usb: cdc-wdm: use memdup

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Date:   Sat, 06 May 2017 19:40:42 +0200
From:   Bjørn Mork <bjorn@...k.no>
To:     Geliang Tang <geliangtang@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Oliver Neukum <oneukum@...e.com>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: cdc-wdm: use memdup_user

Geliang Tang <geliangtang@...il.com> writes:

> Use memdup_user() helper instead of open-coding to simplify the code.
>
> Signed-off-by: Geliang Tang <geliangtang@...il.com>
> ---
>  drivers/usb/class/cdc-wdm.c | 15 +++------------
>  1 file changed, 3 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
> index 08669fe..0e4f18c 100644
> --- a/drivers/usb/class/cdc-wdm.c
> +++ b/drivers/usb/class/cdc-wdm.c
> @@ -361,17 +361,9 @@ static ssize_t wdm_write
>  	if (we < 0)
>  		return usb_translate_errors(we);
>  
> -	buf = kmalloc(count, GFP_KERNEL);
> -	if (!buf) {
> -		rv = -ENOMEM;
> -		goto outnl;
> -	}
> -
> -	r = copy_from_user(buf, buffer, count);
> -	if (r > 0) {
> -		rv = -EFAULT;
> -		goto out_free_mem;
> -	}
> +	buf = memdup_user(buffer, count);
> +	if (IS_ERR(buf))
> +		return PTR_ERR(buf);
>  
>  	/* concurrent writes and disconnect */
>  	r = mutex_lock_interruptible(&desc->wlock);
> @@ -441,7 +433,6 @@ static ssize_t wdm_write
>  
>  	usb_autopm_put_interface(desc->intf);
>  	mutex_unlock(&desc->wlock);
> -outnl:
>  	return rv < 0 ? rv : count;
>  
>  out_free_mem_pm:

Nice!

Please check this, but I believe you can simplify that last return as
well. There is no way to end up there with rv < 0 after you've removed
the label. So

  return count;

should do.


Bjørn