The Linux kernel s390/dasd subsystem had a vulnerability where several sysfs show/store handlers called discipline callbacks that dereferenced device->private before it was allocated. This occurred because the discipline was assigned prior to check_device() allocating device->private during dasd_generic_set_online(). An unprivileged user could trigger a NULL pointer dereference by reading world-readable sysfs attributes in this timing window, resulting in a kernel panic. The vulnerability was fixed by adding guards around the dereferences inside each affected callback.

An unprivileged user could cause a kernel panic by reading certain sysfs attributes during a specific timing window, leading to a denial of service. There is no indication of privilege escalation or code execution. The impact is limited to system stability disruption via a NULL pointer dereference.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is applied, avoid triggering the affected sysfs attributes during device online operations in the s390/dasd subsystem. Monitor vendor channels for official patches or updates.