linux-kernel - Re: [PATCH v3] lib: Use PFN_PHYS() in devmem_is

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Date:   Mon, 2 Aug 2021 15:40:02 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Liang Wang <wangliang101@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     palmerdabbelt@...gle.com, linux-kernel@...r.kernel.org,
        gregkh@...uxfoundation.org, linux@...linux.org.uk,
        linux-arm-kernel@...ts.infradead.org, stable@...r.kernel.org,
        wangle6@...wei.com, kepler.chenxin@...wei.com,
        nixiaoming@...wei.com, wangkefeng.wang@...wei.com
Subject: Re: [PATCH v3] lib: Use PFN_PHYS() in devmem_is_allowed()

On Sat, Jul 31, 2021 at 10:50:57AM +0800, Liang Wang wrote:
> The physical address may exceed 32 bits on 32-bit systems with
> more than 32 bits of physcial address,use PFN_PHYS() in devmem_is_allowed(),
> or the physical address may overflow and be truncated.
> We found this bug when mapping a high addresses through devmem tool,
> when CONFIG_STRICT_DEVMEM is enabled on the ARM with ARM_LPAE and devmem
> is used to map a high address that is not in the iomem address range,
> an unexpected error indicating no permission is returned.
> 
> This bug was initially introduced from v2.6.37, and the function was moved
> to lib when v5.11.
> 
> Cc: Luis Chamberlain <mcgrof@...nel.org>
> 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: Luis Chamberlain <mcgrof@...nel.org>

  Luis