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ARM: smp: add support for per-task stack canaries

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On ARM, we currently only change the value of the stack canary when
switching tasks if the kernel was built for UP. On SMP kernels, this
is impossible since the stack canary value is obtained via a global
symbol reference, which means
a) all running tasks on all CPUs must use the same value
b) we can only modify the value when no kernel stack frames are live
   on any CPU, which is effectively never.

So instead, use a GCC plugin to add a RTL pass that replaces each
reference to the address of the __stack_chk_guard symbol with an
expression that produces the address of the 'stack_canary' field
that is added to struct thread_info. This way, each task will use
its own randomized value.

Cc: Russell King <linux@armlinux.org.uk>
Cc: Kees Cook <keescook@chromium.org>
Cc: Emese Revfy <re.emese@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Laura Abbott <labbott@redhat.com>
Cc: kernel-hardening@lists.openwall.com
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Ard Biesheuvel 2018-12-06 09:32:57 +01:00 • committed by Kees Cook
parent ccda4af0f4
commit 189af46571
10 changed files with 163 additions and 3 deletions
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6
scripts/Makefile.gcc-plugins
View file

@ -36,6 +36,12 @@ ifdef CONFIG_GCC_PLUGIN_STACKLEAK
endif
export DISABLE_STACKLEAK_PLUGIN
gcc-plugin-$(CONFIG_GCC_PLUGIN_ARM_SSP_PER_TASK) += arm_ssp_per_task_plugin.so
ifdef CONFIG_GCC_PLUGIN_ARM_SSP_PER_TASK
DISABLE_ARM_SSP_PER_TASK_PLUGIN += -fplugin-arg-arm_ssp_per_task_plugin-disable
endif
export DISABLE_ARM_SSP_PER_TASK_PLUGIN
# All the plugin CFLAGS are collected here in case a build target needs to
# filter them out of the KBUILD_CFLAGS.
GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y))