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

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Date:   Tue, 03 Aug 2021 22:14:28 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     wangkefeng.wang@...wei.com
CC:     wangliang101@...wei.com, mcgrof@...nel.org,
        linux-kernel@...r.kernel.org, Greg KH <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
Subject:     Re: [PATCH v3] lib: Use PFN_PHYS() in devmem_is_allowed()

On Tue, 03 Aug 2021 22:01:46 PDT (-0700), wangkefeng.wang@...wei.com wrote:
>
> On 2021/7/31 10:50, 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: Kefeng Wang <wangkefeng.wang@...wei.com>

Weird, it's still only your replies that are coming through.  Given that 
this only manifests on 32-bit Arm systems, I'm going to leave this up to 
them for now.

Acked-by: Palmer Dabbelt <palmerdabbelt@...gle.com>