linux-kernel - Re: [PATCH] staging: r8188eu: Use memdup_user instead of kmalloc/copy_from

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Message-ID: <20211210083010.GM1956@kadam>
Date:   Fri, 10 Dec 2021 11:30:10 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
Cc:     Larry.Finger@...inger.net, phil@...lpotter.co.uk,
        gregkh@...uxfoundation.org, linux-staging@...ts.linux.dev,
        linux-kernel@...r.kernel.org, Abaci Robot <abaci@...ux.alibaba.com>
Subject: Re: [PATCH] staging: r8188eu: Use memdup_user instead of
 kmalloc/copy_from_user

On Fri, Dec 10, 2021 at 11:38:32AM +0800, Jiapeng Chong wrote:
> Fix following coccicheck warning:
> 
> ./drivers/staging/r8188eu/os_dep/ioctl_linux.c:4253:8-15: WARNING
> opportunity for memdup_user.
> 
> Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
> Signed-off-by: Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
> ---
>  drivers/staging/r8188eu/os_dep/ioctl_linux.c | 13 ++++---------
>  1 file changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/staging/r8188eu/os_dep/ioctl_linux.c b/drivers/staging/r8188eu/os_dep/ioctl_linux.c
> index 56adfe4087a8..c6a2fbfe8f26 100644
> --- a/drivers/staging/r8188eu/os_dep/ioctl_linux.c
> +++ b/drivers/staging/r8188eu/os_dep/ioctl_linux.c
> @@ -4250,17 +4250,12 @@ static int rtw_test(
>  	DBG_88E("+%s\n", __func__);
>  	len = wrqu->data.length;
>  
> -	pbuf = kzalloc(len, GFP_KERNEL);
> -	if (!pbuf) {
> -		DBG_88E("%s: no memory!\n", __func__);
> -		return -ENOMEM;
> -	}
> -
> -	if (copy_from_user(pbuf, wrqu->data.pointer, len)) {
> -		kfree(pbuf);
> +	pbuf = memdup_user(wrqu->data.pointer, len);

This code assumes that the user is going to give us a NUL terminated
string which is not necessarily true.  The original code was buggy too.
Anyway, please fix it.  Use strndup_user() and mention that it is a bug
fix in the commit message:

	pbuf = strndup_user(wrqu->data.pointer, len);

Add a Fixes tag.

regards,
dan carpenter