linux-kernel - Re: [PATCH] arm64: correct modules range of kernel virtual memory layout

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Message-ID: <CAKv+Gu9qD_-GNHus5txiqj9eHLpU5S7RX8QxYeUG17Ok0QNz-A@mail.gmail.com>
Date:   Mon, 7 Aug 2017 14:18:00 +0100
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Will Deacon <will.deacon@....com>
Cc:     Miles Chen <miles.chen@...iatek.com>,
        Catalin Marinas <catalin.marinas@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-mediatek@...ts.infradead.org, wsd_upstream@...iatek.com
Subject: Re: [PATCH] arm64: correct modules range of kernel virtual memory layout

On 7 August 2017 at 14:16, Will Deacon <will.deacon@....com> wrote:
> On Mon, Aug 07, 2017 at 07:04:46PM +0800, Miles Chen wrote:
>> The commit f80fb3a3d508 ("arm64: add support for kernel ASLR")
>> moved module virtual address to
>> [module_alloc_base, module_alloc_base + MODULES_VSIZE).
>>
>> Display module information of the virtual kernel
>> memory layout by using module_alloc_base.
>>
>> testing output:
>> 1) Current implementation:
>> Virtual kernel memory layout:
>>       modules : 0xffffff8000000000 - 0xffffff8008000000   (   128 MB)
>> 2) this patch + KASLR:
>> Virtual kernel memory layout:
>>       modules : 0xffffff8000560000 - 0xffffff8008560000   (   128 MB)
>> 3) this patch + KASLR and a dummy seed:
>> Virtual kernel memory layout:
>>       modules : 0xffffffa7df637000 - 0xffffffa7e7637000   (   128 MB)
>>
>> Signed-off-by: Miles Chen <miles.chen@...iatek.com>
>> ---
>>  arch/arm64/mm/init.c | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> Does this mean the modules code in our pt dumper is busted
> (arch/arm64/mm/dump.c)? Also, what about KASAN, which uses these addresses
> too (in kasan_init)? Should we just remove MODULES_VADDR and MODULES_END
> altogether?
>

I don't think we need this patch. The 'module' line simply prints the
VA region that is reserved for modules. The fact that we end up
putting them elsewhere when running randomized does not necessarily
mean this line should reflect that.