lkml.org 
[lkml]   [2020]   [Jun]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v4 3/5] stack: Optionally randomize kernel stack offset each syscall
From
Date
On 6/22/20 12:31 PM, Kees Cook wrote:
> This provides the ability for architectures to enable kernel stack base
> address offset randomization. This feature is controlled by the boot
> param "randomize_kstack_offset=on/off", with its default value set by
> CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
>
> Co-developed-by: Elena Reshetova <elena.reshetova@intel.com>
> Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
> Link: https://lore.kernel.org/r/20190415060918.3766-1-elena.reshetova@intel.com
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> Makefile | 4 ++++
> arch/Kconfig | 23 ++++++++++++++++++
> include/linux/randomize_kstack.h | 40 ++++++++++++++++++++++++++++++++
> init/main.c | 23 ++++++++++++++++++
> 4 files changed, 90 insertions(+)
> create mode 100644 include/linux/randomize_kstack.h

Hi,
Please add documentation for the new kernel boot parameter to
Documentation/admin-guide/kernel-parameters.txt.


> diff --git a/arch/Kconfig b/arch/Kconfig
> index 1ea61290900a..1f52c9cfefca 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -883,6 +883,29 @@ config VMAP_STACK
> virtual mappings with real shadow memory, and KASAN_VMALLOC must
> be enabled.
>
> +config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
> + def_bool n
> + help
> + An arch should select this symbol if it can support kernel stack
> + offset randomization with calls to add_random_kstack_offset()
> + during syscall entry and choose_random_kstack_offset() during
> + syscall exit. Downgrading of -fstack-protector-strong to
> + -fstack-protector should also be applied to the entry code and
> + closely examined, as the artificial stack bump looks like an array
> + to the compiler, so it will attempt to add canary checks regardless
> + of the static branch state.
> +
> +config RANDOMIZE_KSTACK_OFFSET_DEFAULT
> + bool "Randomize kernel stack offset on syscall entry"
> + depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
> + help
> + The kernel stack offset can be randomized (after pt_regs) by
> + roughly 5 bits of entropy, frustrating memory corruption
> + attacks that depend on stack address determinism or
> + cross-syscall address exposures. This feature is controlled
> + by kernel boot param "randomize_kstack_offset=on/off", and this
> + config chooses the default boot state.


thanks.
--
~Randy

\
 
 \ /
  Last update: 2020-06-22 21:42    [W:0.114 / U:0.368 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site