Re: [PATCH] staging: r8188eu: Use memdup_user instead of kmalloc/copy_from_user

[Dan Carpenter <dan.carpenter@oracle.com>]

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@linux.alibaba.com>
> Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.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