staging: rtl8188eu: prevent ->ssid overflow in rtw_wx_set_scan()

stable inclusion
from linux-4.19.181
commit eda4378094de16090d74eacea3d8c10f7719ed25
CVE: CVE-2021-28660

--------------------------------

commit 74b6b20df8cfe90ada777d621b54c32e69e27cd7 upstream.

This code has a check to prevent read overflow but it needs another
check to prevent writing beyond the end of the ->ssid[] array.

Fixes: a2c60d42 ("staging: r8188eu: Add files for new driver - part 16")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/YEHymwsnHewzoam7@mwanda


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>