From: Lucas De Marchi <lucas.demarchi@intel.com>
Date: Sat, 8 Mar 2025 01:02:01 +0000 (-0800)
Subject: thermal: core: Delay exposing sysfs interface
X-Git-Tag: io_uring-6.15-20250403~112^2^2
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=ff63b62d5abd2ce109401a8b57d5e36c4b07a5b1;p=linux-block.git

thermal: core: Delay exposing sysfs interface

There's a race between initializing the governor and userspace accessing
the sysfs interface. From time to time the Intel graphics CI shows this
signature:

	<1>[] #PF: error_code(0x0000) - not-present page
	<6>[] PGD 0 P4D 0
	<4>[] Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI
	<4>[] CPU: 3 UID: 0 PID: 562 Comm: thermald Not tainted 6.14.0-rc4-CI_DRM_16208-g7e37396f86d8+ #1
	<4>[] Hardware name: Intel Corporation Twin Lake Client Platform/AlderLake-N LP5 RVP, BIOS TWLNFWI1.R00.5222.A01.2405290634 05/29/2024
	<4>[] RIP: 0010:policy_show+0x1a/0x40

thermald tries to read the policy file between the sysfs files being
created and the governor set by thermal_set_governor(), which causes the
NULL pointer dereference.

Similarly to the hwmon interface, delay exposing the sysfs files to when
the governor is already set.

Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13655
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patch.msgid.link/20250307-thermal-sysfs-race-v1-1-8a3d4d4ac9c4@intel.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 2328ac0d8561..f96ca2710928 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -1589,26 +1589,26 @@ thermal_zone_device_register_with_trips(const char *type,
 
 	tz->state = TZ_STATE_FLAG_INIT;
 
+	result = dev_set_name(&tz->device, "thermal_zone%d", tz->id);
+	if (result)
+		goto remove_id;
+
+	thermal_zone_device_init(tz);
+
+	result = thermal_zone_init_governor(tz);
+	if (result)
+		goto remove_id;
+
 	/* sys I/F */
 	/* Add nodes that are always present via .groups */
 	result = thermal_zone_create_device_groups(tz);
 	if (result)
 		goto remove_id;
 
-	result = dev_set_name(&tz->device, "thermal_zone%d", tz->id);
-	if (result) {
-		thermal_zone_destroy_device_groups(tz);
-		goto remove_id;
-	}
-	thermal_zone_device_init(tz);
 	result = device_register(&tz->device);
 	if (result)
 		goto release_device;
 
-	result = thermal_zone_init_governor(tz);
-	if (result)
-		goto unregister;
-
 	if (!tz->tzp || !tz->tzp->no_hwmon) {
 		result = thermal_add_hwmon_sysfs(tz);
 		if (result)