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Date: Tue, 27 Aug 2019 11:33:51 +1000
From: Michael Ellerman <mpe@...erman.id.au>
To: Scott Wood <oss@...error.net>
Cc: linux-kernel@...r.kernel.org, wangkefeng.wang@...wei.com, yebin10@...wei.com, thunder.leizhen@...wei.com, jingxiangfeng@...wei.com, fanchengyang@...wei.com, zhaohongjiang@...wei.com, Jason Yan <yanaijie@...wei.com>, 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
Subject: Re: [PATCH v6 00/12] implement KASLR for powerpc/fsl_booke/32

Jason Yan <yanaijie@...wei.com> writes:
> A polite ping :)
>
> What else should I do now?

That's a good question.

Scott, are you still maintaining FSL bits, and if so any comments? Or
should I take this.

cheers

> On 2019/8/19 14:12, Jason Yan wrote:
>> Hi Michael,
>> 
>> Is there anything more I should do to get this feature meeting the 
>> requirements of the mainline?
>> 
>> Thanks,
>> Jason
>> 
>> On 2019/8/9 18:07, 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 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_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  |  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          |  12 +-
>>>   arch/powerpc/kernel/fsl_booke_entry_mapping.S |  27 +-
>>>   arch/powerpc/kernel/head_fsl_booke.S          |  55 ++-
>>>   arch/powerpc/kernel/kaslr_booke.c             | 393 ++++++++++++++++++
>>>   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/fsl_booke.c            |   8 +-
>>>   18 files changed, 572 insertions(+), 52 deletions(-)
>>>   create mode 100644 Documentation/powerpc/kaslr-booke32.rst
>>>   create mode 100644 arch/powerpc/kernel/kaslr_booke.c
>>>

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