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thermal/debugfs: Prevent use-after-free from occurring after cdev removal 

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: 755113d767 ("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>
This commit is contained in:
Rafael J. Wysocki 2024-04-26 11:10:10 +02:00
parent c7f7c37271
commit d351eb0ab0
1 changed files with 11 additions and 3 deletions
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14
drivers/thermal/thermal_debugfs.c
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@ -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);