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

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Date:	Fri, 30 Aug 2013 11:15:49 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Maxime Bizon <mbizon@...ebox.fr>
Cc:	Anton Vorontsov <anton@...msg.org>,
	Colin Cross <ccross@...roid.com>,
	Tony Luck <tony.luck@...el.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pstore/ram: (really) fix undefined usage of rounddown_pow_of_two

On Fri, Aug 30, 2013 at 9:06 AM, Maxime Bizon <mbizon@...ebox.fr> wrote:
> Previous attempt to fix was b042e47491ba5f487601b5141a3f1d8582304170
>
> Suggested use of is_power_of_2() was bogus because is_power_of_2(0) is
> false (documented behaviour).
>
> Signed-off-by: Maxime Bizon <mbizon@...ebox.fr>

Yes, excellent point. :)

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

Thanks,

-Kees

> ---
>  fs/pstore/ram.c |    6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
> index a6119f9..03325bc 100644
> --- a/fs/pstore/ram.c
> +++ b/fs/pstore/ram.c
> @@ -400,11 +400,11 @@ static int ramoops_probe(struct platform_device *pdev)
>                 goto fail_out;
>         }
>
> -       if (!is_power_of_2(pdata->record_size))
> +       if (pdata->record_size && !is_power_of_2(pdata->record_size))
>                 pdata->record_size = rounddown_pow_of_two(pdata->record_size);
> -       if (!is_power_of_2(pdata->console_size))
> +       if (pdata->console_size && !is_power_of_2(pdata->console_size))
>                 pdata->console_size = rounddown_pow_of_two(pdata->console_size);
> -       if (!is_power_of_2(pdata->ftrace_size))
> +       if (pdata->ftrace_size && !is_power_of_2(pdata->ftrace_size))
>                 pdata->ftrace_size = rounddown_pow_of_two(pdata->ftrace_size);
>
>         cxt->dump_read_cnt = 0;
> --
> 1.7.9.5
>
>
> --
> Maxime
>
>



-- 
Kees Cook
Chrome OS Security
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