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Date: Wed, 16 Jul 2025 23:23:56 -0700
From: Kees Cook <kees@kernel.org>
To: Tiffany Yang <ynaffit@google.com>
Cc: linux-kernel@vger.kernel.org, kernel-team@android.com,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Arve =?iso-8859-1?B?SGr4bm5lduVn?= <arve@android.com>,
	Todd Kjos <tkjos@android.com>, Martijn Coenen <maco@android.com>,
	Joel Fernandes <joelagnelf@nvidia.com>,
	Christian Brauner <brauner@kernel.org>,
	Carlos Llamas <cmllamas@google.com>,
	Suren Baghdasaryan <surenb@google.com>,
	Brendan Higgins <brendan.higgins@linux.dev>,
	David Gow <davidgow@google.com>, Rae Moar <rmoar@google.com>,
	linux-kselftest@vger.kernel.org, kunit-dev@googlegroups.com
Subject: Re: [PATCH v4 2/6] binder: Store lru freelist in binder_alloc
Message-ID: <202507162323.8A11B97@keescook>
References: <20250717011011.3365074-1-ynaffit@google.com>
 <20250717011011.3365074-3-ynaffit@google.com>
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In-Reply-To: <20250717011011.3365074-3-ynaffit@google.com>

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