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

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Date:   Tue, 29 Oct 2019 11:58:07 -0400
From:   Masayoshi Mizuma <msys.mizuma@...il.com>
To:     Baoquan He <bhe@...hat.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 Baoquan,

On Tue, Oct 29, 2019 at 10:59:20AM +0800, Baoquan He wrote:
> Hi Masa,
> 
> On 08/30/19 at 05:47pm, Masayoshi Mizuma wrote:
> > From: Masayoshi Mizuma <m.mizuma@...fujitsu.com>
> 
> Any plan about this patchset?

Thank you for pinging me and so sorry for the delay.
I'll post the v4 in this week.

Thanks,
Masa

> 
> 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
> > 
>