linux-kernel - Re: [PATCH v2 05/11] drivers/acpi: convert seqno counter

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Message-ID: <202010071116.9D9A5C1416@keescook>
Date:   Wed, 7 Oct 2020 11:16:45 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     rafael@...nel.org, lenb@...nel.org, gregkh@...uxfoundation.org,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 05/11] drivers/acpi: convert seqno counter_atomic32

On Tue, Oct 06, 2020 at 02:44:36PM -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.
> 
> seqno is a sequence number counter for logging. This counter gets
> incremented. Unsure if there is a chance of this overflowing. It
> doesn't look like overflowing causes any problems since it is used
> to tag the log messages and nothing more.
> 
> Convert it to use counter_atomic32.
> 
> This conversion doesn't change the overflow wrap around behavior.
> 
> Acked-by: Rafael J. Wysocki <rafael@...nel.org>
> Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>

Agreed: this looks like logging only.

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

-- 
Kees Cook