6.8-stable review patch. If anyone has any objections, please let me know.
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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);