[PATCH 6.8 050/336] thermal/debugfs: Prevent use-after-free from occurring after cdev removal

Greg Kroah-Hartman
2024-05-14T10:26:14Z

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

[ Upstream commit d351eb0ab04c3e8109895fc33250cebbce9c11da ]

Since thermal_debug_cdev_remove() does not run under cdev->lock, it can
run in parallel with thermal_debug_cdev_state_update() and it may free
the struct thermal_debugfs object used by the latter after it has been
checked against NULL.

If that happens, thermal_debug_cdev_state_update() will access memory
that has been freed already causing the kernel to crash.

Address this by using cdev->lock in thermal_debug_cdev_remove() around
the cdev->debugfs value check (in case the same cdev is removed at the
same time in two different threads) and its reset to NULL.

Fixes: 755113d76786 ("thermal/debugfs: Add thermal cooling device debugfs information")
Cc :6.8+ <stable@vger.kernel.org> # 6.8+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/thermal/thermal_debugfs.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/thermal/thermal_debugfs.c b/drivers/thermal/thermal_debugfs.c
index 1fe2914a8853b..5693cc8b231aa 100644
--- a/drivers/thermal/thermal_debugfs.c
+++ b/drivers/thermal/thermal_debugfs.c
@@ -505,15 +505,23 @@ void thermal_debug_cdev_add(struct thermal_cooling_device *cdev)
*/
void thermal_debug_cdev_remove(struct thermal_cooling_device *cdev)
{
- struct thermal_debugfs *thermal_dbg = cdev->debugfs;
+ struct thermal_debugfs *thermal_dbg;

- if (!thermal_dbg)
+ mutex_lock(&cdev->lock);
+
+ thermal_dbg = cdev->debugfs;
+ if (!thermal_dbg) {
+ mutex_unlock(&cdev->lock);
return;
+ }
+
+ cdev->debugfs = NULL;
+
+ mutex_unlock(&cdev->lock);

mutex_lock(&thermal_dbg->lock);

thermal_debugfs_cdev_clear(&thermal_dbg->cdev_dbg);
- cdev->debugfs = NULL;

mutex_unlock(&thermal_dbg->lock);

--
2.43.0