CVE-2026-64556

In the Linux kernel, the following vulnerability has been resolved:

perf/core: Detach event groups during remove_on_exec

perf_event_remove_on_exec() removes events by calling

perf_event_exit_event(). For top-level events, this removes the event from

the context with DETACH_EXIT only.

This can leave inconsistent group state when a removed event is a group

leader and the group contains siblings without remove_on_exec. If the group

was active, the surviving siblings can remain active and attached to the

removed leader's sibling list, but are no longer represented by a valid

group leader on the PMU context active lists.

A later close of the removed leader uses DETACH_GROUP and can promote the

still-active siblings from this stale group state. The next schedule-in can

then add an already-linked active_list entry again, corrupting the PMU

context active list.

With DEBUG_LIST enabled, this is caught as a list_add double-add in

merge_sched_in().

Fix this by detaching group relationships when remove_on_exec removes an

event. This preserves the existing task-exit and revoke behavior, while

ensuring surviving siblings are ungrouped before the removed event leaves

the context.