Hi! This should be good to go now. :) v10: - switch from "m" to "o" constraint (will) - switch to raw_cpu_*() (tglx) - hooked LKDTM test up to kselftest v9: https://lore.kernel.org/lkml/20210331205458.1871746-1-keescook@xxxxxxxxxxxx/ v8: https://lore.kernel.org/lkml/20210330205750.428816-1-keescook@xxxxxxxxxxxx/ v7: https://lore.kernel.org/lkml/20210319212835.3928492-1-keescook@xxxxxxxxxxxx/ v6: https://lore.kernel.org/lkml/20210315180229.1224655-1-keescook@xxxxxxxxxxxx/ v5: https://lore.kernel.org/lkml/20210309214301.678739-1-keescook@xxxxxxxxxxxx/ v4: https://lore.kernel.org/lkml/20200622193146.2985288-1-keescook@xxxxxxxxxxxx/ v3: https://lore.kernel.org/lkml/20200406231606.37619-1-keescook@xxxxxxxxxxxx/ v2: https://lore.kernel.org/lkml/20200324203231.64324-1-keescook@xxxxxxxxxxxx/ rfc: https://lore.kernel.org/kernel-hardening/20190329081358.30497-1-elena.reshetova@xxxxxxxxx/ This is a continuation and refactoring of Elena's earlier effort to add kernel stack base offset randomization. In the time since the earlier discussions, two attacks[1][2] were made public that depended on stack determinism, so we're no longer in the position of "this is a good idea but we have no examples of attacks". :) Earlier discussions also devolved into debates on entropy sources, which is mostly a red herring, given the already low entropy available due to stack size. Regardless, entropy can be changed/improved separately from this series as needed. Earlier discussions also got stuck debating how much syscall overhead was too much, but this is also a red herring since the feature itself needs to be selectable at boot with no cost for those that don't want it: this is solved here with static branches. So, here is the latest improved version, made as arch-agnostic as possible, with usage added for x86 and arm64. It also includes some small static branch clean ups, and addresses some surprise performance issues due to the stack canary[3]. Thanks! -Kees [1] https://a13xp0p0v.github.io/2020/02/15/CVE-2019-18683.html [2] https://repositorio-aberto.up.pt/bitstream/10216/125357/2/374717.pdf [3] https://lore.kernel.org/lkml/202003281520.A9BFF461@keescook/ Kees Cook (6): jump_label: Provide CONFIG-driven build state defaults init_on_alloc: Optimize static branches stack: Optionally randomize kernel stack offset each syscall x86/entry: Enable random_kstack_offset support arm64: entry: Enable random_kstack_offset support lkdtm: Add REPORT_STACK for checking stack offsets .../admin-guide/kernel-parameters.txt | 11 ++++ Makefile | 4 ++ arch/Kconfig | 23 ++++++++ arch/arm64/Kconfig | 1 + arch/arm64/kernel/Makefile | 5 ++ arch/arm64/kernel/syscall.c | 16 ++++++ arch/x86/Kconfig | 1 + arch/x86/entry/common.c | 3 ++ arch/x86/include/asm/entry-common.h | 16 ++++++ drivers/misc/lkdtm/bugs.c | 17 ++++++ drivers/misc/lkdtm/core.c | 1 + drivers/misc/lkdtm/lkdtm.h | 1 + include/linux/jump_label.h | 19 +++++++ include/linux/mm.h | 10 ++-- include/linux/randomize_kstack.h | 54 +++++++++++++++++++ init/main.c | 23 ++++++++ mm/page_alloc.c | 4 +- mm/slab.h | 6 ++- tools/testing/selftests/lkdtm/.gitignore | 1 + tools/testing/selftests/lkdtm/Makefile | 1 + .../testing/selftests/lkdtm/stack-entropy.sh | 36 +++++++++++++ 21 files changed, 245 insertions(+), 8 deletions(-) create mode 100644 include/linux/randomize_kstack.h create mode 100755 tools/testing/selftests/lkdtm/stack-entropy.sh -- 2.25.1
