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

s390/cio: Fix NULL pointer dereference in ccw_device_get_util_str()

The channel path registry entry associated with a CHPID may be removed
while the subchannel's PMCW still references that CHPID. In this case,
chpid_to_chp() can return NULL, leading to a NULL pointer dereference.

Add the missing NULL check before dereferencing the returned pointer.