linux-kernel - Re: [PATCH v2 03/11] drivers/base: convert deferred_trigger_count and probe_count to counter

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Message-ID: <202010071112.E76FC61D24@keescook>
Date:   Wed, 7 Oct 2020 11:13:27 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     gregkh@...uxfoundation.org, rafael@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 03/11] drivers/base: convert deferred_trigger_count
 and probe_count to counter_atomic32

On Tue, Oct 06, 2020 at 02:44:34PM -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.
> 
> deferred_trigger_count gets incremented and read. It doesn't guard
> object lifetimes, device usage counts, device open counts, and pm
> states. There is very little chance of this counter overflowing.
> Convert it to use counter_atomic32.
> 
> This conversion doesn't change the overflow wrap around behavior.
> 
> probe_count gets incremented, decremented, read. It doesn't guard
> object lifetimes, device usage counts, device open counts, and pm
> states. There is very little chance of this counter overflowing.
> This counter controls the wait for known devices to complete their
> probing, and probe_count == 0 ends the wait. Other than that it
> meets the other criteria to be converted. Convert it to use
> counter_atomic32.
> 
> Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>

With the "wrap around to 0" commit log detail fixed, look good:

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

-- 
Kees Cook