linux-kernel - Re: [PATCH v3 1/6] binder: Fix selftest page indexing

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Message-ID: <202507160726.EC296DBFA@keescook>
Date: Wed, 16 Jul 2025 07:27:24 -0700
From: Kees Cook <kees@...nel.org>
To: Tiffany Yang <ynaffit@...gle.com>
Cc: linux-kernel@...r.kernel.org, kernel-team@...roid.com,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Arve Hjønnevåg <arve@...roid.com>,
	Todd Kjos <tkjos@...roid.com>, Martijn Coenen <maco@...roid.com>,
	Joel Fernandes <joelagnelf@...dia.com>,
	Christian Brauner <brauner@...nel.org>,
	Carlos Llamas <cmllamas@...gle.com>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Brendan Higgins <brendan.higgins@...ux.dev>,
	David Gow <davidgow@...gle.com>, Rae Moar <rmoar@...gle.com>,
	linux-kselftest@...r.kernel.org, kunit-dev@...glegroups.com
Subject: Re: [PATCH v3 1/6] binder: Fix selftest page indexing

On Mon, Jul 14, 2025 at 11:53:14AM -0700, Tiffany Yang wrote:
> The binder allocator selftest was only checking the last page of buffers
> that ended on a page boundary. Correct the page indexing to account for
> buffers that are not page-aligned.
> 
> Signed-off-by: Tiffany Yang <ynaffit@...gle.com>
> ---
>  drivers/android/binder_alloc_selftest.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/android/binder_alloc_selftest.c b/drivers/android/binder_alloc_selftest.c
> index c88735c54848..486af3ec3c02 100644
> --- a/drivers/android/binder_alloc_selftest.c
> +++ b/drivers/android/binder_alloc_selftest.c
> @@ -142,12 +142,12 @@ static void binder_selftest_free_buf(struct binder_alloc *alloc,
>  	for (i = 0; i < BUFFER_NUM; i++)
>  		binder_alloc_free_buf(alloc, buffers[seq[i]]);
>  
> -	for (i = 0; i < end / PAGE_SIZE; i++) {
>  		/**
>  		 * Error message on a free page can be false positive
>  		 * if binder shrinker ran during binder_alloc_free_buf
>  		 * calls above.
>  		 */
> +	for (i = 0; i <= (end - 1) / PAGE_SIZE; i++) {

Nit: this comment is now not aligned correctly. Probably the best would
be the leave the "for" line above the comment.

-Kees

>  		if (list_empty(page_to_lru(alloc->pages[i]))) {
>  			pr_err_size_seq(sizes, seq);
>  			pr_err("expect lru but is %s at page index %d\n",
> -- 
> 2.50.0.727.gbf7dc18ff4-goog
> 

-- 
Kees Cook