drivers/rapidio/rio_cm.c: prevent possible heap overwrite

In the Linux kernel, the following vulnerability has been resolved: drivers/rapidio/rio_cm.c: prevent possible heap overwrite In riocm_cdev_ioctl(RIO_CM_CHAN_SEND) -> cm_chan_msg_send() -> riocm_ch_send() cm_chan_msg_send() checks that userspace didn't send too much data but riocm_ch_send() failed to check that userspace sent sufficient data. The result is that riocm_ch_send() can write to fields in the rio_ch_chan_hdr which were outside the bounds of the space which cm_chan_msg_send() allocated. Address this by teaching riocm_ch_send() to check that the entire rio_ch_chan_hdr was copied in from userspace.