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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Benjamin Tissoires <benjamin.tissoires@redhat.com>,
        Sebastian Reichel <sebastian.reichel@collabora.co.uk>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL 4.14 18/87] power: remove possible deadlock when
 unregistering power_supply
Thread-Topic: [PATCH AUTOSEL 4.14 18/87] power: remove possible deadlock when
 unregistering power_supply
Thread-Index: AQHUTjLiBt/SjjVec0qLGX11K88yzQ==
Date:   Mon, 17 Sep 2018 03:02:35 +0000
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From: Benjamin Tissoires <benjamin.tissoires@redhat.com>

[ Upstream commit 3ffa6583e24e1ad1abab836d24bfc9d2308074e5 ]

If a device gets removed right after having registered a power_supply node,
we might enter in a deadlock between the remove call (that has a lock on
the parent device) and the deferred register work.

Allow the deferred register work to exit without taking the lock when
we are in the remove state.

Stack trace on a Ubuntu 16.04:

[16072.109121] INFO: task kworker/u16:2:1180 blocked for more than 120 seco=
nds.
[16072.109127]       Not tainted 4.13.0-41-generic #46~16.04.1-Ubuntu
[16072.109129] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables =
this message.
[16072.109132] kworker/u16:2   D    0  1180      2 0x80000000
[16072.109142] Workqueue: events_power_efficient power_supply_deferred_regi=
ster_work
[16072.109144] Call Trace:
[16072.109152]  __schedule+0x3d6/0x8b0
[16072.109155]  schedule+0x36/0x80
[16072.109158]  schedule_preempt_disabled+0xe/0x10
[16072.109161]  __mutex_lock.isra.2+0x2ab/0x4e0
[16072.109166]  __mutex_lock_slowpath+0x13/0x20
[16072.109168]  ? __mutex_lock_slowpath+0x13/0x20
[16072.109171]  mutex_lock+0x2f/0x40
[16072.109174]  power_supply_deferred_register_work+0x2b/0x50
[16072.109179]  process_one_work+0x15b/0x410
[16072.109182]  worker_thread+0x4b/0x460
[16072.109186]  kthread+0x10c/0x140
[16072.109189]  ? process_one_work+0x410/0x410
[16072.109191]  ? kthread_create_on_node+0x70/0x70
[16072.109194]  ret_from_fork+0x35/0x40
[16072.109199] INFO: task test:2257 blocked for more than 120 seconds.
[16072.109202]       Not tainted 4.13.0-41-generic #46~16.04.1-Ubuntu
[16072.109204] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables =
this message.
[16072.109206] test            D    0  2257   2256 0x00000004
[16072.109208] Call Trace:
[16072.109211]  __schedule+0x3d6/0x8b0
[16072.109215]  schedule+0x36/0x80
[16072.109218]  schedule_timeout+0x1f3/0x360
[16072.109221]  ? check_preempt_curr+0x5a/0xa0
[16072.109224]  ? ttwu_do_wakeup+0x1e/0x150
[16072.109227]  wait_for_completion+0xb4/0x140
[16072.109230]  ? wait_for_completion+0xb4/0x140
[16072.109233]  ? wake_up_q+0x70/0x70
[16072.109236]  flush_work+0x129/0x1e0
[16072.109240]  ? worker_detach_from_pool+0xb0/0xb0
[16072.109243]  __cancel_work_timer+0x10f/0x190
[16072.109247]  ? device_del+0x264/0x310
[16072.109250]  ? __wake_up+0x44/0x50
[16072.109253]  cancel_delayed_work_sync+0x13/0x20
[16072.109257]  power_supply_unregister+0x37/0xb0
[16072.109260]  devm_power_supply_release+0x11/0x20
[16072.109263]  release_nodes+0x110/0x200
[16072.109266]  devres_release_group+0x7c/0xb0
[16072.109274]  wacom_remove+0xc2/0x110 [wacom]
[16072.109279]  hid_device_remove+0x6e/0xd0 [hid]
[16072.109284]  device_release_driver_internal+0x158/0x210
[16072.109288]  device_release_driver+0x12/0x20
[16072.109291]  bus_remove_device+0xec/0x160
[16072.109293]  device_del+0x1de/0x310
[16072.109298]  hid_destroy_device+0x27/0x60 [hid]
[16072.109303]  usbhid_disconnect+0x51/0x70 [usbhid]
[16072.109308]  usb_unbind_interface+0x77/0x270
[16072.109311]  device_release_driver_internal+0x158/0x210
[16072.109315]  device_release_driver+0x12/0x20
[16072.109318]  usb_driver_release_interface+0x77/0x80
[16072.109321]  proc_ioctl+0x20f/0x250
[16072.109325]  usbdev_do_ioctl+0x57f/0x1140
[16072.109327]  ? __wake_up+0x44/0x50
[16072.109331]  usbdev_ioctl+0xe/0x20
[16072.109336]  do_vfs_ioctl+0xa4/0x600
[16072.109339]  ? vfs_write+0x15a/0x1b0
[16072.109343]  SyS_ioctl+0x79/0x90
[16072.109347]  entry_SYSCALL_64_fastpath+0x24/0xab
[16072.109349] RIP: 0033:0x7f20da807f47
[16072.109351] RSP: 002b:00007ffc422ae398 EFLAGS: 00000246 ORIG_RAX: 000000=
0000000010
[16072.109353] RAX: ffffffffffffffda RBX: 00000000010b8560 RCX: 00007f20da8=
07f47
[16072.109355] RDX: 00007ffc422ae3a0 RSI: 00000000c0105512 RDI: 00000000000=
00009
[16072.109356] RBP: 0000000000000000 R08: 00007ffc422ae3e0 R09: 00000000000=
00010
[16072.109357] R10: 00000000000000a6 R11: 0000000000000246 R12: 00000000000=
00000
[16072.109359] R13: 00000000010b8560 R14: 00007ffc422ae2e0 R15: 00000000000=
00000

Reported-and-tested-by: Richard Hughes <rhughes@redhat.com>
Tested-by: Aaron Skomra <Aaron.Skomra@wacom.com>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Fixes: 7f1a57fdd6cb ("power_supply: Fix possible NULL pointer dereference o=
n early uevent")
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 drivers/power/supply/power_supply_core.c | 11 +++++++++--
 include/linux/power_supply.h             |  1 +
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/suppl=
y/power_supply_core.c
index 02c6340ae36f..3226faebe0a0 100644
--- a/drivers/power/supply/power_supply_core.c
+++ b/drivers/power/supply/power_supply_core.c
@@ -14,6 +14,7 @@
 #include <linux/types.h>
 #include <linux/init.h>
 #include <linux/slab.h>
+#include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/notifier.h>
 #include <linux/err.h>
@@ -139,8 +140,13 @@ static void power_supply_deferred_register_work(struct=
 work_struct *work)
 	struct power_supply *psy =3D container_of(work, struct power_supply,
 						deferred_register_work.work);
=20
-	if (psy->dev.parent)
-		mutex_lock(&psy->dev.parent->mutex);
+	if (psy->dev.parent) {
+		while (!mutex_trylock(&psy->dev.parent->mutex)) {
+			if (psy->removing)
+				return;
+			msleep(10);
+		}
+	}
=20
 	power_supply_changed(psy);
=20
@@ -1071,6 +1077,7 @@ EXPORT_SYMBOL_GPL(devm_power_supply_register_no_ws);
 void power_supply_unregister(struct power_supply *psy)
 {
 	WARN_ON(atomic_dec_return(&psy->use_cnt));
+	psy->removing =3D true;
 	cancel_work_sync(&psy->changed_work);
 	cancel_delayed_work_sync(&psy->deferred_register_work);
 	sysfs_remove_link(&psy->dev.kobj, "powers");
diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
index 79e90b3d3288..4617cf4f6c5b 100644
--- a/include/linux/power_supply.h
+++ b/include/linux/power_supply.h
@@ -251,6 +251,7 @@ struct power_supply {
 	spinlock_t changed_lock;
 	bool changed;
 	bool initialized;
+	bool removing;
 	atomic_t use_cnt;
 #ifdef CONFIG_THERMAL
 	struct thermal_zone_device *tzd;
--=20
2.17.1