CVE-2026-80626

A flaw was found in the Linux kernel's powerpc/perf component. An issue in the fsl_emb_pmu_del() function can lead to a preempt count underflow. This occurs when the function attempts to decrement a preemption counter without a corresponding increment, specifically when event->hw.idx is negative. On systems configured for preemption, this underflow can result in a 'scheduling while atomic' bug, leading to a system crash and a Denial of Service (DoS).

A flaw rated moderate severity by Red Hat Product Security was found in the Linux kernel's PowerPC performance events subsystem. The fsl_emb_pmu_del() function calls put_cpu_var(cpu_hw_events) unconditionally at its exit label, but the matching get_cpu_var() is only called after the early-return check for a negative event->hw.idx. When an event with a negative hardware index is removed, an unmatched preempt_enable() is issued, underflowing preempt_count. On kernels built with CONFIG_PREEMPT=y, this underflow can eventually present as a 'scheduling while atomic' BUG, causing a kernel crash and a local denial of service; a local user with access to the performance events subsystem on affected PowerPC hardware could trigger this condition. Confidentiality and integrity are not impacted. Although the upstream Linux kernel as a whole is affected, all Red Hat Enterprise Linux and Red Hat In-Vehicle OS kernel and kernel-rt components listed in this flaw are not affected because the vulnerable code is not present in the kernels Red Hat ships, so no Red Hat update is required.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.