[PATCH mainline-linux] thermal/core: Populate max_state before setting up cooling dev sysfs

[Ovidiu Panait]

Since commit 13f4e660a126 ("thermal/core:
Split __thermal_cooling_device_register() into two functions"),
thermal_cooling_device_setup_sysfs() is called before the
->get_max_state() callback in thermal_cooling_device_add().
However, cooling_device_stats_setup() allocates space based on
cdev->max_state, which is not initialized at that point.

With CONFIG_THERMAL_STATISTICS=y, an out of bounds access happens
inside thermal_cooling_device_stats_update(), followed by a kernel
crash:

Unable to handle kernel paging request at virtual address ffff800081329e60
Call trace:
 queued_spin_lock_slowpath+0x1cc/0x320 (P)
 thermal_cooling_device_stats_update+0x28/0xa4
 __thermal_cdev_update+0x74/0x88
 thermal_cdev_update+0x44/0x58
 step_wise_manage+0x1b8/0x300
 __thermal_zone_device_update+0x270/0x414
 thermal_zone_device_check+0x28/0x40
 process_one_work+0x150/0x290
 worker_thread+0x18c/0x300
 kthread+0x114/0x120
 ret_from_fork+0x10/0x20

To fix this, restore the original ordering of ->get_max_state() and
thermal_cooling_device_setup_sysfs(). Note that with this reordering,
the dev_set_name() and ->get_max_state() error paths now reach
thermal_cdev_release() without setup_sysfs() having run. This is safe
because cdev->stats is NULL in that case and destroy_sysfs() is a no-op.

Fixes: 13f4e660a126 ("thermal/core: Split __thermal_cooling_device_register() into two functions")
Signed-off-by: Ovidiu Panait <ovidiu.panait.rb@xxxxxxxxxxx>
---
 drivers/thermal/thermal_core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 4e2a17fdb6a7..9b9fa51067bd 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -1015,8 +1015,6 @@ static int thermal_cooling_device_add(struct thermal_cooling_device *cdev, void
 	device_initialize(&cdev->device);
 	cdev->devdata = devdata;
 
-	thermal_cooling_device_setup_sysfs(cdev);
-
 	ret = dev_set_name(&cdev->device, "cooling_device%d", cdev->id);
 	if (ret)
 		goto out_put_device;
@@ -1037,6 +1035,8 @@ static int thermal_cooling_device_add(struct thermal_cooling_device *cdev, void
 	if (ret)
 		current_state = ULONG_MAX;
 
+	thermal_cooling_device_setup_sysfs(cdev);
+
 	ret = device_add(&cdev->device);
 	if (ret)
 		goto out_put_device;
-- 
2.34.1