| Message ID | 20190805064335.19156-1-yanaijie@huawei.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | implement KASLR for powerpc/fsl_booke/32 | expand |
Hi Christophe , Can you take a look at patch 6,7,9 of this version? Thank you, Jason On 2019/8/5 14:43, 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. > > 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 (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 | 27 +- > arch/powerpc/kernel/head_fsl_booke.S | 55 ++- > arch/powerpc/kernel/kaslr_booke.c | 427 ++++++++++++++++++ > arch/powerpc/kernel/machine_kexec.c | 1 + > arch/powerpc/kernel/misc_64.S | 5 - > arch/powerpc/kernel/setup-common.c | 19 + > 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, 560 insertions(+), 50 deletions(-) > create mode 100644 arch/powerpc/kernel/kaslr_booke.c >
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. 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 (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 | 27 +- arch/powerpc/kernel/head_fsl_booke.S | 55 ++- arch/powerpc/kernel/kaslr_booke.c | 427 ++++++++++++++++++ arch/powerpc/kernel/machine_kexec.c | 1 + arch/powerpc/kernel/misc_64.S | 5 - arch/powerpc/kernel/setup-common.c | 19 + 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, 560 insertions(+), 50 deletions(-) create mode 100644 arch/powerpc/kernel/kaslr_booke.c