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randstruct: Reorganize Kconfigs and attribute macros

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In preparation for Clang supporting randstruct, reorganize the Kconfigs,
move the attribute macros, and generalize the feature to be named
CONFIG_RANDSTRUCT for on/off, CONFIG_RANDSTRUCT_FULL for the full
randomization mode, and CONFIG_RANDSTRUCT_PERFORMANCE for the cache-line
sized mode.

Cc: linux-hardening@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220503205503.3054173-4-keescook@chromium.org
This commit is contained in:
Kees Cook
2022-05-03 13:55:00 -07:00
parent d364658970
commit 595b893e20
10 changed files with 81 additions and 66 deletions
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38
scripts/gcc-plugins/Kconfig
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@@ -46,44 +46,6 @@ config GCC_PLUGIN_LATENT_ENTROPY
* https://grsecurity.net/
* https://pax.grsecurity.net/
config GCC_PLUGIN_RANDSTRUCT
bool "Randomize layout of sensitive kernel structures"
select MODVERSIONS if MODULES
help
If you say Y here, the layouts of structures that are entirely
function pointers (and have not been manually annotated with
__no_randomize_layout), or structures that have been explicitly
marked with __randomize_layout, will be randomized at compile-time.
This can introduce the requirement of an additional information
exposure vulnerability for exploits targeting these structure
types.
Enabling this feature will introduce some performance impact,
slightly increase memory usage, and prevent the use of forensic
tools like Volatility against the system (unless the kernel
source tree isn't cleaned after kernel installation).
The seed used for compilation is located at
scripts/gcc-plugins/randomize_layout_seed.h. It remains after
a make clean to allow for external modules to be compiled with
the existing seed and will be removed by a make mrproper or
make distclean.
This plugin was ported from grsecurity/PaX. More information at:
* https://grsecurity.net/
* https://pax.grsecurity.net/
config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE
bool "Use cacheline-aware structure randomization"
depends on GCC_PLUGIN_RANDSTRUCT
depends on !COMPILE_TEST # do not reduce test coverage
help
If you say Y here, the RANDSTRUCT randomization will make a
best effort at restricting randomization to cacheline-sized
groups of elements. It will further not randomize bitfields
in structures. This reduces the performance hit of RANDSTRUCT
at the cost of weakened randomization.
config GCC_PLUGIN_ARM_SSP_PER_TASK
bool
depends on GCC_PLUGINS && ARM