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

In the Linux kernel, the following vulnerability has been resolved:

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.