linux-kernel - [PATCH] perf: Don't enable the perf_event without in PERF_ATTACH

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Date:	Thu,  3 Jul 2014 11:36:38 +0800
From:	Chen LinX <linx.z.chen@...el.com>
To:	a.p.zijlstra@...llo.nl, paulus@...ba.org, mingo@...hat.com,
	acme@...stprotocols.net, linux-kernel@...r.kernel.org
Cc:	yanmin_zhang@...ux.intel.com, "Chen LinX" <linx.z.chen@...el.com>,
	Yanmin Zhang <yanmin.zhang@...el.com>
Subject: [PATCH] perf: Don't enable the perf_event without in PERF_ATTACH_CONTEXT status

From: "Chen LinX" <linx.z.chen@...el.com>

when do cpu hotplug test and run below perf test together, pmu may access freed perf_event

while true;
do
perf record -a -g -f sleep 10
rm perf.*
done

the scenario is that when cpu offline firstly, the 'perf_cpu_notify' will disable event on the
pmu and remove it from the context list. after cpu online, the perf app may enable the event
that without linked in context list again. when cpu offine the second time, the 'perf_cpu_notify'
can't disable event on the pmu as the event doesn't link to context list. the perf app may free
this event later(the free procedure try to disable event on the pmu but as the cpu is offline,
the 'cpu_function_call(event->cpu, __perf_remove_from_context, event)' is failed). then after
cpu online again, pmu will access freed perf_event and hit panic.

so adding PERF_ATTACH_CONTEXT flag check before enable event to avoid this scenario.

[  157.666035 ] BUG: unable to handle kernel paging request at ffffffe89af56004
[  157.666166 ] IP: [<ffffffff8234218c>] do_raw_spin_lock+0xc/0x130
[  157.668086 ] Call Trace:
[  157.668122 ]  <IRQ>
[  157.668156 ]  [<ffffffff828a69aa>] _raw_spin_lock_irqsave+0x2a/0x40
[  157.668268 ]  [<ffffffff820168f0>] __intel_shared_reg_get_constraints.isra.9+0x70/0x150
[  157.668350 ]  [<ffffffff8201762e>] intel_get_event_constraints+0x8e/0x150
[  157.668424 ]  [<ffffffff82011191>] x86_schedule_events+0x81/0x200
[  157.668495 ]  [<ffffffff8201767a>] ? intel_get_event_constraints+0xda/0x150
[  157.668568 ]  [<ffffffff82011191>] ? x86_schedule_events+0x81/0x200
[  157.668640 ]  [<ffffffff82028848>] ? flat_send_IPI_mask+0x88/0xa0
[  157.668710 ]  [<ffffffff820e5628>] ? __enqueue_entity+0x78/0x80
[  157.668777 ]  [<ffffffff820e818a>] ? enqueue_task_fair+0x90a/0xdd0
[  157.668848 ]  [<ffffffff82145585>] ? tracer_tracing_is_on+0x15/0x30
[  157.668918 ]  [<ffffffff820f3b91>] ? cpuacct_charge+0x61/0x70
[  157.668984 ]  [<ffffffff82028848>] ? flat_send_IPI_mask+0x88/0xa0
[  157.669052 ]  [<ffffffff820233c5>] ? native_smp_send_reschedule+0x45/0x60
[  157.669126 ]  [<ffffffff820df199>] ? resched_task+0x69/0x70
[  157.669192 ]  [<ffffffff82145585>] ? tracer_tracing_is_on+0x15/0x30
[  157.669262 ]  [<ffffffff82161c13>] ? perf_pmu_enable+0x13/0x30
[  157.669328 ]  [<ffffffff820102ef>] ? x86_pmu_add+0xaf/0x150
[  157.669393 ]  [<ffffffff8200ffc0>] x86_pmu_commit_txn+0x50/0xa0
[  157.669462 ]  [<ffffffff82008cf4>] ? native_sched_clock+0x24/0x80
[  157.669531 ]  [<ffffffff82008cf4>] ? native_sched_clock+0x24/0x80
[  157.669598 ]  [<ffffffff820e441d>] ? sched_clock_cpu+0xbd/0x110
[  157.669664 ]  [<ffffffff820e44af>] ? local_clock+0x3f/0x50
[  157.669729 ]  [<ffffffff82161fe4>] ? perf_event_update_userpage+0xe4/0x150
[  157.669802 ]  [<ffffffff82162721>] ? event_sched_in.isra.72+0x81/0x190
[  157.669871 ]  [<ffffffff821629ca>] group_sched_in+0x19a/0x1e0
[  157.669937 ]  [<ffffffff82008cf4>] ? native_sched_clock+0x24/0x80
[  157.670006 ]  [<ffffffff82162bc8>] ctx_sched_in+0x1b8/0x1e0
[  157.670071 ]  [<ffffffff821630c2>] perf_event_sched_in+0x22/0x80
[  157.670138 ]  [<ffffffff8216321f>] __perf_install_in_context+0xff/0x170
[  157.670212 ]  [<ffffffff8215e8ab>] remote_function+0x4b/0x60
[  157.670282 ]  [<ffffffff821086bd>] generic_smp_call_function_single_interrupt+0x9d/0x120
[  157.670363 ]  [<ffffffff82339e79>] ? __const_udelay+0x29/0x30
[  157.670429 ]  [<ffffffff820236b7>] smp_call_function_single_interrupt+0x27/0x40
[  157.670504 ]  [<ffffffff828ad96f>] call_function_single_interrupt+0x6f/0x80

Change-Id: I7265d83159b9180e9be3a370ba50e067385547bd
Signed-off-by: Yanmin Zhang <yanmin.zhang@...el.com>
Signed-off-by: Chen LinX <linx.z.chen@...el.com>
---
 kernel/events/core.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index e76e495..30f0095 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1783,7 +1783,7 @@ static int __perf_event_enable(void *info)
 	 * where the task could be killed and 'ctx' deactivated
 	 * by perf_event_exit_task.
 	 */
-	if (!ctx->is_active)
+	if (!ctx->is_active || !(event->attach_state & PERF_ATTACH_CONTEXT))
 		return -EINVAL;
 
 	raw_spin_lock(&ctx->lock);
-- 
1.7.9.5

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