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perf/core: Fix NULL pmu_ctx passed to pmu->sched_task()

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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.

Fixes: bd27568117 ("perf: Rewrite core context handling")
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Yifan Wu <wuyifan50@huawei.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260810133540.1947118-2-puranjay@kernel.org
This commit is contained in:
Puranjay Mohan 2026-08-10 06:35:34 -07:00 committed by Peter Zijlstra
parent cca4980630
commit 36bb85cf36
1 changed files with 1 additions and 1 deletions
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kernel/events/core.c
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@ -3914,7 +3914,7 @@ static void __perf_pmu_sched_task(struct perf_cpu_pmu_context *cpc,
perf_ctx_lock(cpuctx, cpuctx->task_ctx);
perf_pmu_disable(pmu);
pmu->sched_task(cpc->task_epc, task, sched_in);
pmu->sched_task(&cpc->epc, task, sched_in);
perf_pmu_enable(pmu);
perf_ctx_unlock(cpuctx, cpuctx->task_ctx);