USB: serial: io_edgeport: handle unbound ports on URB completion

[ Upstream commit e37d1aeda737a20b1846a91a3da3f8b0f00cf690 ]

Check for NULL port data in the shared interrupt and bulk completion
callbacks to avoid dereferencing a NULL pointer in case a device sends
data for a port device which isn't bound to a driver (e.g. due to a
malicious device having unexpected endpoints or after an allocation
failure on port probe).

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Cc: stable <stable@vger.kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>