linux-kernel - Re: [PATCH v3 1/1] arm64: mm: correct the inside linear map range during hotplug check

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Date:   Fri, 19 Feb 2021 19:18:07 +0000
From:   Will Deacon <will@...nel.org>
To:     Pavel Tatashin <pasha.tatashin@...een.com>
Cc:     tyhicks@...ux.microsoft.com, jmorris@...ei.org,
        catalin.marinas@....com, akpm@...ux-foundation.org,
        anshuman.khandual@....com, rppt@...nel.org, logang@...tatee.com,
        ardb@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, mhocko@...e.com, linux-mm@...ck.org
Subject: Re: [PATCH v3 1/1] arm64: mm: correct the inside linear map range
 during hotplug check

On Tue, Feb 16, 2021 at 10:03:51AM -0500, Pavel Tatashin wrote:
> Memory hotplug may fail on systems with CONFIG_RANDOMIZE_BASE because the
> linear map range is not checked correctly.
> 
> The start physical address that linear map covers can be actually at the
> end of the range because of randomization. Check that and if so reduce it
> to 0.
> 
> This can be verified on QEMU with setting kaslr-seed to ~0ul:
> 
> memstart_offset_seed = 0xffff
> START: __pa(_PAGE_OFFSET(vabits_actual)) = ffff9000c0000000
> END:   __pa(PAGE_END - 1) =  1000bfffffff
> 
> Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>
> Fixes: 58284a901b42 ("arm64/mm: Validate hotplug range before creating linear mapping")
> Tested-by: Tyler Hicks <tyhicks@...ux.microsoft.com>
> ---
>  arch/arm64/mm/mmu.c | 21 +++++++++++++++++++--
>  1 file changed, 19 insertions(+), 2 deletions(-)

I tried to queue this as a fix, but unfortunately it doesn't apply.
Please can you send a v4 based on the arm64 for-next/fixes branch?

Thanks,

Will