Linux perf/x86 - event pointer setup ordering in x86_pmu_enable(): A NULL pointer dereference in the x86 PMU enable

Impact

A NULL pointer dereference in the x86 PMU enable path, reported from a production AMD EPYC system. Performance counters are enabled by every profiling and observability agent on a fleet, so this crashes hosts through the monitoring stack rather than through anything a tenant did - and it takes co-resident GPU jobs with it.

Who can reach it

Local, through perf event enablement. Reachable by whatever has perf access, which on many clusters includes node-level observability agents and, if perf_event_paranoid is relaxed, tenants.

What to do

Fixed in the Linux kernel. Take the distro kernel update (RHEL/Rocky, Ubuntu, SLES) and reboot the host - no firmware, VBIOS or AGESA step. On a GPU fleet this is a cordon, drain and rolling reboot; plan it as normal kernel maintenance. Check perf_event_paranoid on GPU nodes: if you have loosened it so tenants can profile their own kernels - which is a reasonable thing to want on an AI cluster - you have also widened who can reach this.

References