Re: [PATCH v4 2/6] binder: Store lru freelist in binder_alloc

[Kees Cook <kees@kernel.org>]

On Wed, Jul 16, 2025 at 06:10:05PM -0700, Tiffany Yang wrote:
> Store a pointer to the free pages list that the binder allocator should
> use for a process inside of struct binder_alloc. This change allows
> binder allocator code to be tested and debugged deterministically while
> a system is using binder; i.e., without interfering with other binder
> processes and independently of the shrinker. This is necessary to
> convert the current binder_alloc_selftest into a kunit test that does
> not rely on hijacking an existing binder_proc to run.
> 
> A binder process's binder_alloc->freelist should not be changed after
> it is initialized. A sole exception is the process that runs the
> existing binder_alloc selftest. Its freelist can be temporarily replaced
> for the duration of the test because it runs as a single thread before
> any pages can be added to the global binder freelist, and the test frees
> every page it allocates before dropping the binder_selftest_lock. This
> exception allows the existing selftest to be used to check for
> regressions, but it will be dropped when the binder_alloc tests are
> converted to kunit in a subsequent patch in this series.
> 
> Acked-by: Carlos Llamas <cmllamas@google.com>
> Signed-off-by: Tiffany Yang <ynaffit@google.com>

Reviewed-by: Kees Cook <kees@kernel.org>

-- 
Kees Cook