linux-kernel - Re: [PATCH v2] pstore/ram: fix undefined usage of rounddown_pow_of

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Message-ID: <CAGXu5jJhsQ+yGgNRd-sitsusGsuyTjc_Q3DcoSDg4Q=MnJ4agw@mail.gmail.com>
Date:	Mon, 22 Oct 2012 08:17:27 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Florian Fainelli <ffainelli@...ebox.fr>
Cc:	cbouatmailru@...il.com, ccross@...roid.com, tony.luck@...el.com,
	linux-kernel@...r.kernel.org, Maxime Bizon <mbizon@...ebox.fr>,
	stable@...r.kernel.org
Subject: Re: [PATCH v2] pstore/ram: fix undefined usage of rounddown_pow_of_two(0)

On Mon, Oct 22, 2012 at 2:19 AM, Florian Fainelli <ffainelli@...ebox.fr> wrote:
> From: Maxime Bizon <mbizon@...ebox.fr>
>
> record_size / console_size / ftrace_size can be 0 (this is how you
> disable the feature), but rounddown_pow_of_two(0) is undefined. As suggested
> by Kees Cook, use !is_power_of_2() as a condition to call rounddown_pow_of_two
> and avoid its undefined behavior on the value 0. This issue has been present
> since commit 1894a253 (ramoops: Move to fs/pstore/ram.c).
>
> CC: stable@...r.kernel.org
> Signed-off-by: Maxime Bizon <mbizon@...ebox.fr>
> Signed-off-by: Florian Fainelli <ffainelli@...ebox.fr>

Thanks for the fix!

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

-Kees

-- 
Kees Cook
Chrome OS Security
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