usb: typec: ucsi: ccg: reject firmware images without a ':' record header

usb: typec: ucsi: ccg: reject firmware images without a ':' record header

do_flash() locates the first .cyacd record with

	p = strnchr(fw->data, fw->size, ':');
	while (p < eof) {
		s = strnchr(p + 1, eof - p - 1, ':');
		...
	}

If the firmware image contains no ':' byte,  strnchr() returns NULL.
NULL compares less than the valid kernel pointer eof, so the loop body
runs and strnchr() is called with p + 1 == (void *)1 and a length of
roughly (unsigned long)eof, causing a wonderful crash.

The not_signed_fw fallthrough earlier in do_flash() and the chip-state
branches in ccg_fw_update_needed() allow an unsigned blob to reach this
loop, so a root user who can place a crafted file under /lib/firmware
and write the do_flash sysfs attribute can trigger the oops.

Bail out with -EINVAL when the initial strnchr() returns NULL.

Assisted-by: gkh_clanker_t1000
Cc: stable <stable@kernel.org>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://patch.msgid.link/2026051405-posture-shrill-7884@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>