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

perf/core: Fix NULL pmu ctx passed to pmu->sched task()

perf pmu sched task() returns early when cpuctx->task ctx is set, and cpc->task epc is only non-NULL while a task context is scheduled in on this CPU. perf pmu sched task() therefore always passes NULL:

Unable to handle kernel NULL pointer dereference at virtual address 00 pc : armv8pmu sched task+0x14/0x50 Call trace: armv8pmu sched task+0x14/0x50 (P) perf pmu sched task+0xac/0x108 perf event task sched out+0x6c/0xe0

Pass &cpc->epc instead, the CPU-wide context for this PMU, which the function already dereferences a few lines up to find pmu.

armv8pmu sched task() is the only in-tree implementation that dereferences the argument, and it only reads ->pmu, so the oops needs BRBE, added in v6.17.