linux-kernel - Re: [PATCH] [Backport for stable 5.11] arm64: mm: correct the inside linear map boundaries during hotplug check

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Date:   Tue, 30 Mar 2021 13:08:26 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Pavel Tatashin <pasha.tatashin@...een.com>
Cc:     tyhicks@...ux.microsoft.com, jmorris@...ei.org, will@...nel.org,
        anshuman.khandual@....com, ardb@...nel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        gregkh@...uxfoundation.org
Subject: Re: [PATCH] [Backport for stable 5.11] arm64: mm: correct the inside
 linear map boundaries during hotplug check

On Mon, Mar 29, 2021 at 10:28:47AM -0400, Pavel Tatashin wrote:
>commit ee7febce051945be28ad86d16a15886f878204de upstream.
>
>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
>
>Fixes: 58284a901b42 ("arm64/mm: Validate hotplug range before creating linear mapping")
>Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>
>Tested-by: Tyler Hicks <tyhicks@...ux.microsoft.com>
>Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>

Queued up, thanks!

-- 
Thanks,
Sasha