ksmbd: fix integer overflows on 32 bit systems

commit aab98e2d upstream.

On 32bit systems the addition operations in ipc_msg_alloc() can
potentially overflow leading to memory corruption.
Add bounds checking using KSMBD_IPC_MAX_PAYLOAD to avoid overflow.

Fixes: 0626e664 ("cifsd: add server handler for central processing and tranport layers")
Cc: stable@vger.kernel.org
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>