hwmon: Fix double-free in __hwmon_device_register()

Fix double-free that happens when thermal zone setup fails, see KASAN log below.

==================================================================

BUG: KASAN: double-free or invalid-free in __hwmon_device_register+0x5dc/0xa7c

CPU: 0 PID: 132 Comm: kworker/0:2 Tainted: G    B             4.19.0-rc8-next-20181016-00042-gb52cd80401e9-dirty #41
Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
Workqueue: events deferred_probe_work_func
Backtrace:
[<c0110540>] (dump_backtrace) from [<c0110944>] (show_stack+0x20/0x24)
[<c0110924>] (show_stack) from [<c105cb08>] (dump_stack+0x9c/0xb0)
[<c105ca6c>] (dump_stack) from [<c02fdaec>] (print_address_description+0x68/0x250)
[<c02fda84>] (print_address_description) from [<c02fd4ac>] (kasan_report_invalid_free+0x68/0x88)
[<c02fd444>] (kasan_report_invalid_free) from [<c02fc85c>] (__kasan_slab_free+0x1f4/0x200)
[<c02fc668>] (__kasan_slab_free) from [<c02fd0c0>] (kasan_slab_free+0x14/0x18)
[<c02fd0ac>] (kasan_slab_free) from [<c02f9c6c>] (kfree+0x90/0x294)
[<c02f9bdc>] (kfree) from [<c0b41bbc>] (__hwmon_device_register+0x5dc/0xa7c)
[<c0b415e0>] (__hwmon_device_register) from [<c0b421e8>] (hwmon_device_register_with_info+0xa0/0xa8)
[<c0b42148>] (hwmon_device_register_with_info) from [<c0b42324>] (devm_hwmon_device_register_with_info+0x74/0xb4)
[<c0b422b0>] (devm_hwmon_device_register_with_info) from [<c0b4481c>] (lm90_probe+0x414/0x578)
[<c0b44408>] (lm90_probe) from [<c0aeeff4>] (i2c_device_probe+0x35c/0x384)
[<c0aeec98>] (i2c_device_probe) from [<c08776cc>] (really_probe+0x290/0x3e4)
[<c087743c>] (really_probe) from [<c0877a2c>] (driver_probe_device+0x80/0x1c4)
[<c08779ac>] (driver_probe_device) from [<c0877da8>] (__device_attach_driver+0x104/0x11c)
[<c0877ca4>] (__device_attach_driver) from [<c0874dd8>] (bus_for_each_drv+0xa4/0xc8)
[<c0874d34>] (bus_for_each_drv) from [<c08773b0>] (__device_attach+0xf0/0x15c)
[<c08772c0>] (__device_attach) from [<c0877e24>] (device_initial_probe+0x1c/0x20)
[<c0877e08>] (device_initial_probe) from [<c08762f4>] (bus_probe_device+0xdc/0xec)
[<c0876218>] (bus_probe_device) from [<c0876a08>] (deferred_probe_work_func+0xa8/0xd4)
[<c0876960>] (deferred_probe_work_func) from [<c01527c4>] (process_one_work+0x3dc/0x96c)
[<c01523e8>] (process_one_work) from [<c01541e0>] (worker_thread+0x4ec/0x8bc)
[<c0153cf4>] (worker_thread) from [<c015b238>] (kthread+0x230/0x240)
[<c015b008>] (kthread) from [<c01010bc>] (ret_from_fork+0x14/0x38)
Exception stack(0xcf743fb0 to 0xcf743ff8)

3fa0: 00000000 00000000 00000000 00000000
3fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 3fe0: 00000000 00000000 00000000 00000000 00000013 00000000

Allocated by task 132:
 kasan_kmalloc.part.1+0x58/0xf4
 kasan_kmalloc+0x90/0xa4
 kmem_cache_alloc_trace+0x90/0x2a0
 __hwmon_device_register+0xbc/0xa7c
 hwmon_device_register_with_info+0xa0/0xa8
 devm_hwmon_device_register_with_info+0x74/0xb4
 lm90_probe+0x414/0x578
 i2c_device_probe+0x35c/0x384
 really_probe+0x290/0x3e4
 driver_probe_device+0x80/0x1c4
 __device_attach_driver+0x104/0x11c
 bus_for_each_drv+0xa4/0xc8
 __device_attach+0xf0/0x15c
 device_initial_probe+0x1c/0x20
 bus_probe_device+0xdc/0xec
 deferred_probe_work_func+0xa8/0xd4
 process_one_work+0x3dc/0x96c
 worker_thread+0x4ec/0x8bc
 kthread+0x230/0x240
 ret_from_fork+0x14/0x38
   (null)

Freed by task 132:
 __kasan_slab_free+0x12c/0x200
 kasan_slab_free+0x14/0x18
 kfree+0x90/0x294
 hwmon_dev_release+0x1c/0x20
 device_release+0x4c/0xe8
 kobject_put+0xac/0x11c
 device_unregister+0x2c/0x30
 __hwmon_device_register+0xa58/0xa7c
 hwmon_device_register_with_info+0xa0/0xa8
 devm_hwmon_device_register_with_info+0x74/0xb4
 lm90_probe+0x414/0x578
 i2c_device_probe+0x35c/0x384
 really_probe+0x290/0x3e4
 driver_probe_device+0x80/0x1c4
 __device_attach_driver+0x104/0x11c
 bus_for_each_drv+0xa4/0xc8
 __device_attach+0xf0/0x15c
 device_initial_probe+0x1c/0x20
 bus_probe_device+0xdc/0xec
 deferred_probe_work_func+0xa8/0xd4
 process_one_work+0x3dc/0x96c
 worker_thread+0x4ec/0x8bc
 kthread+0x230/0x240
 ret_from_fork+0x14/0x38
   (null)

Cc <[email protected]> # v4.15+

Fixes 47c332deb8e8 ("hwmon: Deal with errors from the thermal subsystem")

Signed-off-by Dmitry Osipenko <[email protected]>

---
 drivers/hwmon/hwmon.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

drivers/hwmon/hwmon.c +4 -2

index 975c95169884..84f61cec6319 100644
@@ -649,8 +649,10 @@ __hwmon_device_register(struct device *dev,  
 const char *name, void *drvdata,
 				if (info[i]->config[j] & HWMON_T_INPUT) {
 					err = hwmon_thermal_add_sensor(dev,
 								hwdev, j);
-					if (err)
-						goto free_device;
+					if (err) {
+						device_unregister(hdev);
+						goto ida_remove;
+					}
 				}
 			}

drivers/hwmon/hwmon.c +0 -2

 		}

@@ -658,8 +660,6 @@ __hwmon_device_register(struct device *dev,  
 const char *name, void *drvdata,
 
 	return hdev;
 
-free_device:
-	device_unregister(hdev);
 free_hwmon:
 	kfree(hwdev);

ida_remove:
--
2.19.0

Quoting Dmitry Osipenko <[email protected]>:

Quoted 3 lines

Fix double-free that happens when thermal zone setup fails, see KASAN log below.

Good catch. I'll apply this as soon as I manage to convince AT&T to restore my internet service.