linux-kernel - Re: [PATCH v3 0/5] Adjust the padding size for KASLR

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Message-ID: <20191029025920.GO8527@MiWiFi-R3L-srv>
Date:   Tue, 29 Oct 2019 10:59:20 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Masayoshi Mizuma <msys.mizuma@...il.com>
Cc:     Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Masayoshi Mizuma <m.mizuma@...fujitsu.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/5] Adjust the padding size for KASLR

Hi Masa,

On 08/30/19 at 05:47pm, Masayoshi Mizuma wrote:
> From: Masayoshi Mizuma <m.mizuma@...fujitsu.com>

Any plan about this patchset?

Thanks
Baoquan

> 
> The system sometimes crashes while memory hot-adding on KASLR
> enabled system. The crash happens because the regions pointed by
> kaslr_regions[].base are overwritten by the hot-added memory.
> 
> It happens because of the padding size for kaslr_regions[].base isn't
> enough for the system whose physical memory layout has huge space for
> memory hotplug. kaslr_regions[].base points "actual installed
> memory size + padding" or higher address. So, if the "actual + padding"
> is lower address than the maximum memory address, which means the memory
> address reachable by memory hot-add, kaslr_regions[].base is destroyed by
> the overwritten.
> 
>   address
>     ^
>     |------- maximum memory address (Hotplug)
>     |                                    ^
>     |------- kaslr_regions[0].base       | Hotadd-able region
>     |     ^                              |
>     |     | padding                      |
>     |     V                              V
>     |------- actual memory address (Installed on boot)
>     |
> 
> Fix it by getting the maximum memory address from SRAT and store
> the value in boot_param, then set the padding size while KASLR
> initializing if the default padding size isn't enough.
> 
> Masayoshi Mizuma (5):
>   x86/boot: Wrap up the SRAT traversing code into subtable_parse()
>   x86/boot: Add max_addr field in struct boot_params
>   x86/boot: Get the max address from SRAT
>   x86/mm/KASLR: Cleanup calculation for direct mapping size
>   x86/mm/KASLR: Adjust the padding size for the direct mapping.
> 
>  Documentation/x86/zero-page.rst       |  4 ++
>  arch/x86/boot/compressed/acpi.c       | 33 +++++++++---
>  arch/x86/include/uapi/asm/bootparam.h |  2 +-
>  arch/x86/mm/kaslr.c                   | 77 +++++++++++++++++++++------
>  4 files changed, 93 insertions(+), 23 deletions(-)
> 
> -- 
> 2.18.1
>