staging: ks7010: potential buffer overflow in ks_wlan_set_encode_ext()

The "exc->key_len" is a u16 that comes from the user.  If it's over
IW_ENCODING_TOKEN_MAX (64) that could lead to memory corruption.

Fixes: b121d848

 ("staging: ks7010: simplify calls to memcpy()")
Cc: stable <stable@kernel.org>
Signed-off-by: Zhang Shurong <zhang_shurong@foxmail.com>
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/tencent_5153B668C0283CAA15AA518325346E026A09@qq.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>