6.13-stable review patch. If anyone has any objections, please let me know.
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From: Vaibhav Jain vaibhav@linux.ibm.com
[ Upstream commit ff99d5b6a246715f2257123cdf6c4a29cb33aa78 ]
Commit 176cda0619b6 ("powerpc/perf: Add perf interface to expose vpa counters") introduced 'vpa_pmu' to expose Book3s-HV nested APIv2 provided L1<->L2 context switch latency counters to L1 user-space via perf-events. However the newly introduced PMU named 'vpa_pmu' doesn't assign ownership of the PMU to the module 'vpa_pmu'. Consequently the module 'vpa_pmu' can be unloaded while one of the perf-events are still active, which can lead to kernel oops and panic of the form below on a Pseries-LPAR:
BUG: Kernel NULL pointer dereference on read at 0x00000058 <snip> NIP [c000000000506cb8] event_sched_out+0x40/0x258 LR [c00000000050e8a4] __perf_remove_from_context+0x7c/0x2b0 Call Trace: [c00000025fc3fc30] [c00000025f8457a8] 0xc00000025f8457a8 (unreliable) [c00000025fc3fc80] [fffffffffffffee0] 0xfffffffffffffee0 [c00000025fc3fcd0] [c000000000501e70] event_function+0xa8/0x120 <snip> Kernel panic - not syncing: Aiee, killing interrupt handler!
Fix this by adding the module ownership to 'vpa_pmu' so that the module 'vpa_pmu' is ref-counted and prevented from being unloaded when perf-events are initialized.
Fixes: 176cda0619b6 ("powerpc/perf: Add perf interface to expose vpa counters") Signed-off-by: Vaibhav Jain vaibhav@linux.ibm.com Signed-off-by: Madhavan Srinivasan maddy@linux.ibm.com Link: https://patch.msgid.link/20250204153527.125491-1-vaibhav@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/perf/vpa-pmu.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/powerpc/perf/vpa-pmu.c b/arch/powerpc/perf/vpa-pmu.c index 6a5bfd2a13b5a..8407334689596 100644 --- a/arch/powerpc/perf/vpa-pmu.c +++ b/arch/powerpc/perf/vpa-pmu.c @@ -156,6 +156,7 @@ static void vpa_pmu_del(struct perf_event *event, int flags) }
static struct pmu vpa_pmu = { + .module = THIS_MODULE, .task_ctx_nr = perf_sw_context, .name = "vpa_pmu", .event_init = vpa_pmu_event_init,