CVE-2026-72176: mm/damon/sysfs-schemes: put stats for scheme_add_dirs() internal error

In the Linux kernel, the following vulnerability has been resolved:

mm/damon/sysfs-schemes: put stats for schemeadddirs() internal error

damonsysfsschemeadddirs() setup the triedregions directory after the stats directory setup is completed. When the triedregions directory setup is failed, the setup function ensures the reference for the tried regions directory is released. Hence the error path should put references on setup succeeded directory objects, starting from the stats directory. However, the error path is putting the triedregions directory instead of the stats directory.

As a direct result, the stats directory object is leaked. Worse yet, if the triedregions directory setup failed from the initial allocation, the scheme->triedregions field remains uninitialized. The following kobjectput(&scheme->triedregions->kobj) call in the error path will dereference the uninitialized memory. The setup failures should not be common. But once it happens, the consequence is quite bad.

Fix this issue by correctly putting the stats directory instead of the triedregions directory.

The issue was discovered [1] by Sashiko.