[PATCH] hwmon: (coretemp) Fix core_data leak on CPUs without PTS

pdata->core_data is allocated in init_temp_data() when the first core
temp_data of a package is created, but it is only released from
destroy_temp_data(), and only in the branch that handles the package
temp_data.

Package temp_data is created solely when the CPU supports
X86_FEATURE_PTS. On a CPU without it, coretemp_cpu_online() never calls
coretemp_add_core() with pkg_flag set, so pdata->pkg_data stays NULL.
coretemp_cpu_offline() then skips the removal of the package interface,
destroy_temp_data() is never called for package data, and the array is
still allocated when coretemp_device_remove() frees the platform data
that pointed at it.

Release the array in coretemp_device_remove(). destroy_temp_data() sets
pdata->core_data to NULL when it frees it, so the added kfree() is a
no-op on CPUs that do have PTS.

Tested on an Intel Core i5-1135G7. The driver was instrumented to log
every allocation and release of pdata->core_data, and the PTS check in
coretemp_cpu_online() was patched out to emulate a CPU without package
thermal support. Without this change the array was allocated and never
released, and coretemp_device_remove() still saw a non-NULL pointer.
With it the array is released and the pointer accounting balances. On an
unmodified build the release still happens via the package temp_data and
the added kfree() sees NULL, with no slab warnings over repeated module
load and unload cycles.

Fixes: 1a793caf6f69 ("hwmon: (coretemp) Use dynamic allocated memory for core temp_data")
Signed-off-by: Szymon Wilczek <[email protected]>
---
 drivers/hwmon/coretemp.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
index 6215ea49faaa..ab9c8cbf887a 100644
--- a/drivers/hwmon/coretemp.c
+++ b/drivers/hwmon/coretemp.c
@@ -650,6 +650,7 @@ static void coretemp_device_remove(int zoneid)
 	struct platform_data *pdata = platform_get_drvdata(pdev);
 
 	ida_destroy(&pdata->ida);
+	kfree(pdata->core_data);
 	kfree(pdata);
 	platform_device_unregister(pdev);
 }

base-commit: d58772d8520c7ef247c4b95c9bd76d3a25da9ff5
prerequisite-patch-id: 1c584cb0c0bb331df7601073d4f307fec3fcd585
-- 
2.55.0