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Message-ID: <c4769b34-95f6-81b9-4856-50459630aa0d@huawei.com>
Date: Wed, 9 Oct 2019 14:10:27 +0800
From: Jason Yan <yanaijie@...wei.com>
To: <mpe@...erman.id.au>, <linuxppc-dev@...ts.ozlabs.org>,
<diana.craciun@....com>, <christophe.leroy@....fr>,
<benh@...nel.crashing.org>, <paulus@...ba.org>, <npiggin@...il.com>,
<keescook@...omium.org>, <kernel-hardening@...ts.openwall.com>,
<oss@...error.net>
CC: <linux-kernel@...r.kernel.org>, <wangkefeng.wang@...wei.com>,
<yebin10@...wei.com>, <thunder.leizhen@...wei.com>,
<jingxiangfeng@...wei.com>, <zhaohongjiang@...wei.com>
Subject: Re: [PATCH v7 00/12] implement KASLR for powerpc/fsl_booke/32
Hi Scott,
Would you please take sometime to test this?
Thank you so much.
On 2019/9/24 13:52, Jason Yan wrote:
> Hi Scott,
>
> Can you test v7 to see if it works to load a kernel at a non-zero address?
>
> Thanks,
>
> On 2019/9/20 17:45, 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 <-----|
>>
>> kernstart_virt_addr
>>
>> 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.
>>
>> Changes since v6:
>> - Rename create_tlb_entry() to create_kaslr_tlb_entry()
>> - Remove MAS2_VAL since there is no more users.
>> - Move kaslr_booke.c to arch/powerpc/mm/nohash.
>> - Call flush_icache_range() after copying the kernel.
>> - Warning if no kaslr-seed provided by the bootloader
>> - Use the right physical address when checking if the new position
>> will overlap with other regions.
>> - Do not clear bss for the second pass because some global variables
>> will not be initialized again
>> - Use tabs instead of spaces between the mnemonic and the
>> arguments(in fsl_booke_entry_mapping.S).
>>
>> Changes since v5:
>> - Rename M_IF_NEEDED to MAS2_M_IF_NEEDED
>> - Define some global variable as __ro_after_init
>> - Replace kimage_vaddr with kernstart_virt_addr
>> - Depend on RELOCATABLE, not select it
>> - Modify the comment block below the SPDX tag
>> - Remove some useless headers in kaslr_booke.c and move is_second_reloc
>> declarationto mmu_decl.h
>> - Remove DBG() and use pr_debug() and rewrite comment above
>> get_boot_seed().
>> - Add a patch to document the KASLR implementation.
>> - Split a patch from patch #10 which exports kaslr offset in
>> VMCOREINFO ELF notes.
>> - Remove extra logic around finding nokaslr string in cmdline.
>> - Make regions static global and __initdata
>>
>> Changes since v4:
>> - Add Reviewed-by tag from Christophe
>> - Remove an unnecessary cast
>> - Remove unnecessary parenthesis
>> - Fix checkpatch warning
>>
>> Changes since v3:
>> - Add Reviewed-by and Tested-by tag from Diana
>> - Change the comment in fsl_booke_entry_mapping.S to be consistent
>> with the new code.
>>
>> Changes since v2:
>> - Remove unnecessary #ifdef
>> - Use SZ_64M instead of0x4000000
>> - Call early_init_dt_scan_chosen() to init boot_command_line
>> - Rename kaslr_second_init() to kaslr_late_init()
>>
>> Changes since v1:
>> - Remove some useless 'extern' keyword.
>> - Replace EXPORT_SYMBOL with EXPORT_SYMBOL_GPL
>> - Improve some assembly code
>> - Use memzero_explicit instead of memset
>> - Use boot_command_line and remove early_command_line
>> - Do not print kaslr offset if kaslr is disabled
>>
>> Jason Yan (12):
>> powerpc: unify definition of M_IF_NEEDED
>> powerpc: move memstart_addr and kernstart_addr to init-common.c
>> powerpc: introduce kernstart_virt_addr to store the kernel base
>> powerpc/fsl_booke/32: introduce create_kaslr_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
>> powerpc/fsl_booke/kaslr: export offset in VMCOREINFO ELF notes
>> powerpc/fsl_booke/32: Document KASLR implementation
>>
>> Documentation/powerpc/kaslr-booke32.rst | 42 ++
>> arch/powerpc/Kconfig | 11 +
>> arch/powerpc/include/asm/nohash/mmu-book3e.h | 11 +-
>> arch/powerpc/include/asm/page.h | 7 +
>> arch/powerpc/kernel/early_32.c | 5 +-
>> arch/powerpc/kernel/exceptions-64e.S | 12 +-
>> arch/powerpc/kernel/fsl_booke_entry_mapping.S | 25 +-
>> arch/powerpc/kernel/head_fsl_booke.S | 61 ++-
>> arch/powerpc/kernel/machine_kexec.c | 1 +
>> arch/powerpc/kernel/misc_64.S | 7 +-
>> arch/powerpc/kernel/setup-common.c | 20 +
>> 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 | 11 +
>> arch/powerpc/mm/nohash/Makefile | 1 +
>> arch/powerpc/mm/nohash/fsl_booke.c | 8 +-
>> arch/powerpc/mm/nohash/kaslr_booke.c | 401 ++++++++++++++++++
>> 18 files changed, 587 insertions(+), 53 deletions(-)
>> create mode 100644 Documentation/powerpc/kaslr-booke32.rst
>> create mode 100644 arch/powerpc/mm/nohash/kaslr_booke.c
>>
>
>
> .
>
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