linux-kernel - Re: [PATCH] usb: gadget: f_fs: use memdup

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Date:   Sat, 13 May 2017 11:05:30 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Geliang Tang <geliangtang@...il.com>
Cc:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Michal Nazarewicz <mina86@...a86.com>,
        Vincent Pelletier <plr.vincent@...il.com>,
        Felix Hädicke <felixhaedicke@....de>,
        Jim Lin <jilin@...dia.com>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: gadget: f_fs: use memdup_user

On Sat, May 13, 2017 at 11:15:59AM +0800, Geliang Tang wrote:
> Use memdup_user() helper instead of open-coding to simplify the code.
> 
> Signed-off-by: Geliang Tang <geliangtang@...il.com>
> ---
>  drivers/usb/gadget/function/f_fs.c | 11 +++--------
>  1 file changed, 3 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> index 71dd27c..5754538 100644
> --- a/drivers/usb/gadget/function/f_fs.c
> +++ b/drivers/usb/gadget/function/f_fs.c
> @@ -3692,14 +3692,9 @@ static char *ffs_prepare_buffer(const char __user *buf, size_t len)
>  	if (unlikely(!len))
>  		return NULL;
>  
> -	data = kmalloc(len, GFP_KERNEL);
> -	if (unlikely(!data))
> -		return ERR_PTR(-ENOMEM);
> -
> -	if (unlikely(copy_from_user(data, buf, len))) {
> -		kfree(data);
> -		return ERR_PTR(-EFAULT);
> -	}
> +	data = memdup_user(buf, len);
> +	if (unlikely(IS_ERR(data)))

Don't use likely/unlikely() here.  It's not a fast path.

regards,
dan carpenter