linux-kernel - [PATCH v6 0/4] Adjust the padding size for KASLR

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Message-Id: <20191206165707.20806-1-msys.mizuma@gmail.com>
Date:   Fri,  6 Dec 2019 11:57:03 -0500
From:   Masayoshi Mizuma <msys.mizuma@...il.com>
To:     Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Baoquan He <bhe@...hat.com>
Cc:     Masayoshi Mizuma <msys.mizuma@...il.com>,
        Masayoshi Mizuma <m.mizuma@...fujitsu.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v6 0/4] Adjust the padding size for KASLR

From: Masayoshi Mizuma <m.mizuma@...fujitsu.com>

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.

Changelog:
    v6: - Add documents to top of calc_direct_mapping_size() to
          explain why the size of direct mapping area is configured
          as boot_params.max_addr (0004 patch).
        - Add Acked-by from Baoquan (0004 patch).

Masayoshi Mizuma (4):
  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: Adjust the padding size for the direct mapping.

 Documentation/x86/zero-page.rst       |  4 ++
 arch/x86/boot/compressed/acpi.c       | 42 +++++++++++++++---
 arch/x86/include/uapi/asm/bootparam.h |  2 +-
 arch/x86/mm/kaslr.c                   | 63 ++++++++++++++++++++-------
 4 files changed, 88 insertions(+), 23 deletions(-)

-- 
2.20.1