linux-kernel - [tip:perf/urgent] perf/core: Protect PMU device removal with a 'pmu_bus_running' check, to fix CONFIG_DEBUG_TEST_DRIVER

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Date:   Fri, 28 Oct 2016 03:10:03 -0700
From:   tip-bot for Jiri Olsa <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     peterz@...radead.org, mingo@...nel.org, jolsa@...hat.com,
        kan.liang@...el.com, caiqian@...hat.com,
        gregkh@...uxfoundation.org, tglx@...utronix.de, robh@...nel.org,
        torvalds@...ux-foundation.org, alexander.shishkin@...ux.intel.com,
        acme@...hat.com, linux-kernel@...r.kernel.org, jolsa@...nel.org,
        hpa@...or.com
Subject: [tip:perf/urgent] perf/core: Protect PMU device removal with a
 'pmu_bus_running' check, to fix CONFIG_DEBUG_TEST_DRIVER_REMOVE=y kernel
 panic

Commit-ID:  0933840acf7b65d6d30a5b6089d882afea57aca3
Gitweb:     http://git.kernel.org/tip/0933840acf7b65d6d30a5b6089d882afea57aca3
Author:     Jiri Olsa <jolsa@...hat.com>
AuthorDate: Thu, 20 Oct 2016 13:10:11 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 28 Oct 2016 11:06:25 +0200

perf/core: Protect PMU device removal with a 'pmu_bus_running' check, to fix CONFIG_DEBUG_TEST_DRIVER_REMOVE=y kernel panic

CAI Qian reported a crash in the PMU uncore device removal code,
enabled by the CONFIG_DEBUG_TEST_DRIVER_REMOVE=y option:

  https://marc.info/?l=linux-kernel&m=147688837328451

The reason for the crash is that perf_pmu_unregister() tries to remove
a PMU device which is not added at this point. We add PMU devices
only after pmu_bus is registered, which happens in the
perf_event_sysfs_init() call and sets the 'pmu_bus_running' flag.

The fix is to get the 'pmu_bus_running' flag state at the point
the PMU is taken out of the PMU list and remove the device
later only if it's set.

Reported-by: CAI Qian <caiqian@...hat.com>
Tested-by: CAI Qian <caiqian@...hat.com>
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Kan Liang <kan.liang@...el.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rob Herring <robh@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/20161020111011.GA13361@krava
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/events/core.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index c6e47e9..a5d2e62 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8855,7 +8855,10 @@ EXPORT_SYMBOL_GPL(perf_pmu_register);
 
 void perf_pmu_unregister(struct pmu *pmu)
 {
+	int remove_device;
+
 	mutex_lock(&pmus_lock);
+	remove_device = pmu_bus_running;
 	list_del_rcu(&pmu->entry);
 	mutex_unlock(&pmus_lock);
 
@@ -8869,10 +8872,12 @@ void perf_pmu_unregister(struct pmu *pmu)
 	free_percpu(pmu->pmu_disable_count);
 	if (pmu->type >= PERF_TYPE_MAX)
 		idr_remove(&pmu_idr, pmu->type);
-	if (pmu->nr_addr_filters)
-		device_remove_file(pmu->dev, &dev_attr_nr_addr_filters);
-	device_del(pmu->dev);
-	put_device(pmu->dev);
+	if (remove_device) {
+		if (pmu->nr_addr_filters)
+			device_remove_file(pmu->dev, &dev_attr_nr_addr_filters);
+		device_del(pmu->dev);
+		put_device(pmu->dev);
+	}
 	free_pmu_context(pmu);
 }
 EXPORT_SYMBOL_GPL(perf_pmu_unregister);