Re: [PATCH] s390/cio: Fix NULL dereference in ccw_device_get_util_str()

[Peter Oberparleiter <oberpar@linux.ibm.com>]

On 22.09.2026 22:48, Vineeth Vijayan wrote:
> 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.

Actually as I understand it, it is the other way around: the registry
(css->chps) still contains the entry, but the PMCW CHPID list contains 0
due a cleared SCHIB. Therefore the lookup will return NULL, unless by
chance a CHPID 0 exists.

> Add the missing NULL check before dereferencing the returned pointer.
> 
> Fixes: 199652309a4d ("s390/cio: add helper to query utility strings per given ccw device")
> Cc: stable@vger.kernel.org
> Signed-off-by: Vineeth Vijayan <vneethv@linux.ibm.com>

Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>


-- 
Peter Oberparleiter
Linux on IBM Z Development - IBM Germany R&D