This vulnerability arises from improper handling of the preemption counter when reading certain sysfs files in the powerpc/hv-gpci subsystem. The bug causes preempt_disable() to be called without a matching put_cpu_var() on successful reads, gradually disabling preemption. Eventually a page fault in user mode triggers faulthandler_disabled, leading to a SIGSEGV and a BUG: scheduling while atomic, which typically results in a kernel crash or core dump. The impact is a local denial of service that can be triggered by reading the affected sysfs attributes and does not provide direct code execution.

The flaw exists in the Linux kernel for configurations where CONFIG_PREEMPT is enabled. It affects all kernels that include the listed sysfs show handlers (processor_bus_topology_show, processor_config_show, affinity_domain_via_virtual_processor_show, and affinity_domain_via_domain_show). The patch is applied to the kernel's powerpc/hv-gpci subsystem; therefore any distribution running a kernel built from this source tree and with PREEMPT enabled is vulnerable. The CPE indicates the Linux kernel broadly.

The CVSS score of 5.5 indicates moderate severity. With an EPSS score below 1% the likelihood of exploitation is very low and the vulnerability is not in the CISA KEV catalog. The required conditions are a local user able to read the affected sysfs entries on a PREEMPT-enabled kernel. An attacker can trigger the crash by issuing repeated reads; there is no authentication bypass or privilege escalation involved and no known exploits have been observed.