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Date: Fri, 26 Jul 2019 07:04:31 +0000
From: Diana Madalina Craciun <diana.craciun@....com>
To: Jason Yan <yanaijie@...wei.com>, "mpe@...erman.id.au"
<mpe@...erman.id.au>, "linuxppc-dev@...ts.ozlabs.org"
<linuxppc-dev@...ts.ozlabs.org>, "christophe.leroy@....fr"
<christophe.leroy@....fr>, "benh@...nel.crashing.org"
<benh@...nel.crashing.org>, "paulus@...ba.org" <paulus@...ba.org>,
"npiggin@...il.com" <npiggin@...il.com>, "keescook@...omium.org"
<keescook@...omium.org>, "kernel-hardening@...ts.openwall.com"
<kernel-hardening@...ts.openwall.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"wangkefeng.wang@...wei.com" <wangkefeng.wang@...wei.com>,
"yebin10@...wei.com" <yebin10@...wei.com>, "thunder.leizhen@...wei.com"
<thunder.leizhen@...wei.com>, "jingxiangfeng@...wei.com"
<jingxiangfeng@...wei.com>, "fanchengyang@...wei.com"
<fanchengyang@...wei.com>, Laurentiu Tudor <laurentiu.tudor@....com>
Subject: Re: [RFC PATCH 00/10] implement KASLR for powerpc/fsl_booke/32
Hi Jason,
I have briefly tested yesterday on a P4080 board and did not see any
issues. I do not have much expertise on KASLR, but I will take a look
over the code.
Regards,
Diana
On 7/25/2019 10:16 AM, Jason Yan wrote:
> Hi all, any comments?
>
>
> On 2019/7/17 16:06, Jason Yan wrote:
>> This series implements KASLR for powerpc/fsl_booke/32, as a security
>> feature that deters exploit attempts relying on knowledge of the location
>> of kernel internals.
>>
>> Since CONFIG_RELOCATABLE has already supported, what we need to do is
>> map or copy kernel to a proper place and relocate. Freescale Book-E
>> parts expect lowmem to be mapped by fixed TLB entries(TLB1). The TLB1
>> entries are not suitable to map the kernel directly in a randomized
>> region, so we chose to copy the kernel to a proper place and restart to
>> relocate.
>>
>> Entropy is derived from the banner and timer base, which will change every
>> build and boot. This not so much safe so additionally the bootloader may
>> pass entropy via the /chosen/kaslr-seed node in device tree.
>>
>> We will use the first 512M of the low memory to randomize the kernel
>> image. The memory will be split in 64M zones. We will use the lower 8
>> bit of the entropy to decide the index of the 64M zone. Then we chose a
>> 16K aligned offset inside the 64M zone to put the kernel in.
>>
>> KERNELBASE
>>
>> |--> 64M <--|
>> | |
>> +---------------+ +----------------+---------------+
>> | |....| |kernel| | |
>> +---------------+ +----------------+---------------+
>> | |
>> |-----> offset <-----|
>>
>> kimage_vaddr
>>
>> We also check if we will overlap with some areas like the dtb area, the
>> initrd area or the crashkernel area. If we cannot find a proper area,
>> kaslr will be disabled and boot from the original kernel.
>>
>> Jason Yan (10):
>> powerpc: unify definition of M_IF_NEEDED
>> powerpc: move memstart_addr and kernstart_addr to init-common.c
>> powerpc: introduce kimage_vaddr to store the kernel base
>> powerpc/fsl_booke/32: introduce create_tlb_entry() helper
>> powerpc/fsl_booke/32: introduce reloc_kernel_entry() helper
>> powerpc/fsl_booke/32: implement KASLR infrastructure
>> powerpc/fsl_booke/32: randomize the kernel image offset
>> powerpc/fsl_booke/kaslr: clear the original kernel if randomized
>> powerpc/fsl_booke/kaslr: support nokaslr cmdline parameter
>> powerpc/fsl_booke/kaslr: dump out kernel offset information on panic
>>
>> arch/powerpc/Kconfig | 11 +
>> arch/powerpc/include/asm/nohash/mmu-book3e.h | 10 +
>> arch/powerpc/include/asm/page.h | 7 +
>> arch/powerpc/kernel/Makefile | 1 +
>> arch/powerpc/kernel/early_32.c | 2 +-
>> arch/powerpc/kernel/exceptions-64e.S | 10 -
>> arch/powerpc/kernel/fsl_booke_entry_mapping.S | 23 +-
>> arch/powerpc/kernel/head_fsl_booke.S | 61 ++-
>> arch/powerpc/kernel/kaslr_booke.c | 439 ++++++++++++++++++
>> arch/powerpc/kernel/machine_kexec.c | 1 +
>> arch/powerpc/kernel/misc_64.S | 5 -
>> arch/powerpc/kernel/setup-common.c | 23 +
>> arch/powerpc/mm/init-common.c | 7 +
>> arch/powerpc/mm/init_32.c | 5 -
>> arch/powerpc/mm/init_64.c | 5 -
>> arch/powerpc/mm/mmu_decl.h | 10 +
>> arch/powerpc/mm/nohash/fsl_booke.c | 8 +-
>> 17 files changed, 580 insertions(+), 48 deletions(-)
>> create mode 100644 arch/powerpc/kernel/kaslr_booke.c
>>
>
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