linux-kernel - Re: [PATCH v2] lib: Use PFN_PHYS() in devmem_is

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Date:   Fri, 30 Jul 2021 15:04:05 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Liang Wang <wangliang101@...wei.com>, <palmerdabbelt@...gle.com>,
        <mcgrof@...nel.org>, <linux-kernel@...r.kernel.org>,
        <gregkh@...uxfoundation.org>, <linux@...linux.org.uk>,
        <linux-arm-kernel@...ts.infradead.org>
CC:     <stable@...r.kernel.org>, <wangle6@...wei.com>,
        <kepler.chenxin@...wei.com>, <nixiaoming@...wei.com>
Subject: Re: [PATCH v2] lib: Use PFN_PHYS() in devmem_is_allowed()


On 2021/7/30 14:49, Liang Wang wrote:
> The physical address may exceed 32 bits on ARM(when ARM_LPAE enabled),
> use PFN_PHYS() in devmem_is_allowed(), or the physical address may
> overflow and be truncated.
>
> This bug was initially introduced from v2.6.37, and the function was moved
> to lib when v5.10.
>
> Fixes: 087aaffcdf9c ("ARM: implement CONFIG_STRICT_DEVMEM by disabling access to RAM via /dev/mem")
> Fixes: 527701eda5f1 ("lib: Add a generic version of devmem_is_allowed()")
> Cc: stable@...r.kernel.org # v2.6.37
> Signed-off-by: Liang Wang <wangliang101@...wei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@...wei.com>
> ---
> v2: update subject and changelog
>   lib/devmem_is_allowed.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/devmem_is_allowed.c b/lib/devmem_is_allowed.c
> index c0d67c541849..60be9e24bd57 100644
> --- a/lib/devmem_is_allowed.c
> +++ b/lib/devmem_is_allowed.c
> @@ -19,7 +19,7 @@
>    */
>   int devmem_is_allowed(unsigned long pfn)
>   {
> -	if (iomem_is_exclusive(pfn << PAGE_SHIFT))
> +	if (iomem_is_exclusive(PFN_PHYS(pfn)))
>   		return 0;
>   	if (!page_is_ram(pfn))
>   		return 1;