linux-kernel - Re: [PATCH v2 07/11] drivers/android/binder: convert stats, transaction_log to counter

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Message-ID: <202010071118.2ADCE5D@keescook>
Date:   Wed, 7 Oct 2020 11:18:25 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     gregkh@...uxfoundation.org, arve@...roid.com, tkjos@...roid.com,
        maco@...roid.com, joel@...lfernandes.org, christian@...uner.io,
        hridya@...gle.com, surenb@...gle.com, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 07/11] drivers/android/binder: convert stats,
 transaction_log to counter_atomic32

On Tue, Oct 06, 2020 at 02:44:38PM -0600, Shuah Khan wrote:
> counter_atomic* is introduced to be used when a variable is used as
> a simple counter and doesn't guard object lifetimes. This clearly
> differentiates atomic_t usages that guard object lifetimes.
> 
> counter_atomic* variables will wrap around to 0 when it overflows and
> should not be used to guard resource lifetimes, device usage and
> open counts that control state changes, and pm states.
> 
> stats tracks per-process binder statistics. Unsure if there is a chance
> of this overflowing, other than stats getting reset to 0. Convert it to
> use counter_atomic.
> 
> binder_transaction_log:cur is used to keep track of the current log entry
> location. Overflow is handled in the code. Since it is used as a
> counter, convert it to use counter_atomic32.
> 
> This conversion doesn't change the overflow wrap around behavior.
> 
> Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>

Yup, seems to be stats-only.

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook