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

From: Will Deacon <will@kernel.org>
To: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: tyhicks@linux.microsoft.com, jmorris@namei.org,
	catalin.marinas@arm.com, akpm@linux-foundation.org,
	anshuman.khandual@arm.com, rppt@kernel.org, logang@deltatee.com,
	ardb@kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, mhocko@suse.com,
	linux-mm@kvack.org
Subject: Re: [PATCH v3 1/1] arm64: mm: correct the inside linear map range during hotplug check
Date: Fri, 19 Feb 2021 19:18:07 +0000	[thread overview]
Message-ID: <20210219191807.GB6683@willie-the-truck> (raw)
In-Reply-To: <20210216150351.129018-2-pasha.tatashin@soleen.com>

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@soleen.com>
> Fixes: 58284a901b42 ("arm64/mm: Validate hotplug range before creating linear mapping")
> Tested-by: Tyler Hicks <tyhicks@linux.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