[PATCH] thermal: add thermal_zone_remove_device_groups()

[Yasuaki Ishimatsu]

When offlining all cores on a CPU, the following system panic
occurs:

BUG: unable to handle kernel NULL pointer dereference at (null)
IP: strlen+0x0/0x20
<snip>
Call Trace:
 ? kernfs_name_hash+0x17/0x80
 kernfs_find_ns+0x3f/0xd0
 kernfs_remove_by_name_ns+0x36/0xa0
 remove_files.isra.1+0x36/0x70
 sysfs_remove_group+0x44/0x90
 sysfs_remove_groups+0x2e/0x50
 device_remove_attrs+0x5e/0x90
 device_del+0x1ea/0x350
 device_unregister+0x1a/0x60
 thermal_zone_device_unregister+0x1f2/0x210
 pkg_thermal_cpu_offline+0x14f/0x1a0 [x86_pkg_temp_thermal]
 ? kzalloc.constprop.2+0x10/0x10 [x86_pkg_temp_thermal]
 cpuhp_invoke_callback+0x8d/0x3f0
 cpuhp_down_callbacks+0x42/0x80
 cpuhp_thread_fun+0x8b/0xf0
 smpboot_thread_fn+0x110/0x160
 kthread+0x101/0x140
 ? sort_range+0x30/0x30
 ? kthread_park+0x90/0x90
 ret_from_fork+0x25/0x30

thermal_zone_create_device_group() sets attribute_groups in
thermal_zone_attribute_groups[] to tz->device.groups. But these
attributes_groups do not have name argument.

So when offlining all cores on CPU and executing
thermal_zone_device_unregister(), the panic occurs in strlen()
called from kernfs_name_hash() because name argument is NULL.

The patch adds thermal_zone_remove_device_groups() to free
tz->device.groups and set NULL pointer.

Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
CC: Zhang Rui <rui.zhang@xxxxxxxxx>
CC: Eduardo Valentin <edubezval@xxxxxxxxx>
---
 drivers/thermal/thermal_core.c  | 3 ++-
 drivers/thermal/thermal_core.h  | 1 +
 drivers/thermal/thermal_sysfs.c | 6 ++++++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 641faab..926e385 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -1251,6 +1251,7 @@ struct thermal_zone_device *

 unregister:
 	release_idr(&thermal_tz_idr, &thermal_idr_lock, tz->id);
+	thermal_zone_remove_device_groups(tz);
 	device_unregister(&tz->device);
 	return ERR_PTR(result);
 }
@@ -1315,8 +1316,8 @@ void thermal_zone_device_unregister(struct thermal_zone_device *tz)
 	release_idr(&thermal_tz_idr, &thermal_idr_lock, tz->id);
 	idr_destroy(&tz->idr);
 	mutex_destroy(&tz->lock);
+	thermal_zone_remove_device_groups(tz);
 	device_unregister(&tz->device);
-	kfree(tz->device.groups);
 }
 EXPORT_SYMBOL_GPL(thermal_zone_device_unregister);

diff --git a/drivers/thermal/thermal_core.h b/drivers/thermal/thermal_core.h
index 2412b37..e3a60db 100644
--- a/drivers/thermal/thermal_core.h
+++ b/drivers/thermal/thermal_core.h
@@ -70,6 +70,7 @@ void thermal_zone_device_unbind_exception(struct thermal_zone_device *,
 int thermal_build_list_of_policies(char *buf);

 /* sysfs I/F */
+void thermal_zone_remove_device_groups(struct thermal_zone_device *tz);
 int thermal_zone_create_device_groups(struct thermal_zone_device *, int);
 void thermal_cooling_device_setup_sysfs(struct thermal_cooling_device *);
 /* used only at binding time */
diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
index a694de9..3dfd29b 100644
--- a/drivers/thermal/thermal_sysfs.c
+++ b/drivers/thermal/thermal_sysfs.c
@@ -605,6 +605,12 @@ static int create_trip_attrs(struct thermal_zone_device *tz, int mask)
 	return 0;
 }

+void thermal_zone_remove_device_groups(struct thermal_zone_device *tz)
+{
+	kfree(tz->device.groups);
+	tz->device.groups = NULL;
+}
+
 int thermal_zone_create_device_groups(struct thermal_zone_device *tz,
 				      int mask)
 {
--
1.8.3.1