fc5e40ccb8
When GCC_PLUGIN_STRUCTLEAK was backported, a prompt text mysteriously
made its way into the Kconfig option. Because this option is not
dependent on GCC_PLUGINS, it could become enabled even when building
with "CC=clang allmodconfig", which is not correct. The option is
correctly selected by GCC_PLUGIN_STRUCTLEAK_BYREF_ALL so this prompt
text seems to be unnecessary.
This change also aligns the help text to match upstream, to match the
version that was claimed to have been backported.
Fixes: e0c6791d04 ("BACKPORT: security: Create "kernel hardening" config area")
Bug: 143965122
Test: make CC=clang allmodconfig && make -j
Change-Id: Ia9dc88ec1bbfd3950eda5a3eb698ecd41c7e0c9a
Signed-off-by: Alistair Delva <adelva@google.com>
114 lines
4.4 KiB
Text
114 lines
4.4 KiB
Text
# SPDX-License-Identifier: GPL-2.0-only
|
|
menu "Kernel hardening options"
|
|
|
|
config GCC_PLUGIN_STRUCTLEAK
|
|
bool
|
|
help
|
|
While the kernel is built with warnings enabled for any missed
|
|
stack variable initializations, this warning is silenced for
|
|
anything passed by reference to another function, under the
|
|
occasionally misguided assumption that the function will do
|
|
the initialization. As this regularly leads to exploitable
|
|
flaws, this plugin is available to identify and zero-initialize
|
|
such variables, depending on the chosen level of coverage.
|
|
|
|
This plugin was originally ported from grsecurity/PaX. More
|
|
information at:
|
|
* https://grsecurity.net/
|
|
* https://pax.grsecurity.net/
|
|
|
|
menu "Memory initialization"
|
|
|
|
config CC_HAS_AUTO_VAR_INIT
|
|
def_bool $(cc-option,-ftrivial-auto-var-init=pattern)
|
|
|
|
choice
|
|
prompt "Initialize kernel stack variables at function entry"
|
|
default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL if COMPILE_TEST && GCC_PLUGINS
|
|
default INIT_STACK_ALL if COMPILE_TEST && CC_HAS_AUTO_VAR_INIT
|
|
default INIT_STACK_NONE
|
|
help
|
|
This option enables initialization of stack variables at
|
|
function entry time. This has the possibility to have the
|
|
greatest coverage (since all functions can have their
|
|
variables initialized), but the performance impact depends
|
|
on the function calling complexity of a given workload's
|
|
syscalls.
|
|
|
|
This chooses the level of coverage over classes of potentially
|
|
uninitialized variables. The selected class will be
|
|
initialized before use in a function.
|
|
|
|
config INIT_STACK_NONE
|
|
bool "no automatic initialization (weakest)"
|
|
help
|
|
Disable automatic stack variable initialization.
|
|
This leaves the kernel vulnerable to the standard
|
|
classes of uninitialized stack variable exploits
|
|
and information exposures.
|
|
|
|
config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
|
|
bool "zero-init anything passed by reference (very strong)"
|
|
depends on GCC_PLUGINS
|
|
select GCC_PLUGIN_STRUCTLEAK
|
|
help
|
|
Zero-initialize any stack variables that may be passed
|
|
by reference and had not already been explicitly
|
|
initialized. This is intended to eliminate all classes
|
|
of uninitialized stack variable exploits and information
|
|
exposures.
|
|
|
|
config INIT_STACK_ALL
|
|
bool "0xAA-init everything on the stack (strongest)"
|
|
depends on CC_HAS_AUTO_VAR_INIT
|
|
help
|
|
Initializes everything on the stack with a 0xAA
|
|
pattern. This is intended to eliminate all classes
|
|
of uninitialized stack variable exploits and information
|
|
exposures, even variables that were warned to have been
|
|
left uninitialized.
|
|
|
|
endchoice
|
|
|
|
config GCC_PLUGIN_STRUCTLEAK_VERBOSE
|
|
bool "Report forcefully initialized variables"
|
|
depends on GCC_PLUGIN_STRUCTLEAK
|
|
depends on !COMPILE_TEST # too noisy
|
|
help
|
|
This option will cause a warning to be printed each time the
|
|
structleak plugin finds a variable it thinks needs to be
|
|
initialized. Since not all existing initializers are detected
|
|
by the plugin, this can produce false positive warnings.
|
|
|
|
config INIT_ON_ALLOC_DEFAULT_ON
|
|
bool "Enable heap memory zeroing on allocation by default"
|
|
help
|
|
This has the effect of setting "init_on_alloc=1" on the kernel
|
|
command line. This can be disabled with "init_on_alloc=0".
|
|
When "init_on_alloc" is enabled, all page allocator and slab
|
|
allocator memory will be zeroed when allocated, eliminating
|
|
many kinds of "uninitialized heap memory" flaws, especially
|
|
heap content exposures. The performance impact varies by
|
|
workload, but most cases see <1% impact. Some synthetic
|
|
workloads have measured as high as 7%.
|
|
|
|
config INIT_ON_FREE_DEFAULT_ON
|
|
bool "Enable heap memory zeroing on free by default"
|
|
help
|
|
This has the effect of setting "init_on_free=1" on the kernel
|
|
command line. This can be disabled with "init_on_free=0".
|
|
Similar to "init_on_alloc", when "init_on_free" is enabled,
|
|
all page allocator and slab allocator memory will be zeroed
|
|
when freed, eliminating many kinds of "uninitialized heap memory"
|
|
flaws, especially heap content exposures. The primary difference
|
|
with "init_on_free" is that data lifetime in memory is reduced,
|
|
as anything freed is wiped immediately, making live forensics or
|
|
cold boot memory attacks unable to recover freed memory contents.
|
|
The performance impact varies by workload, but is more expensive
|
|
than "init_on_alloc" due to the negative cache effects of
|
|
touching "cold" memory areas. Most cases see 3-5% impact. Some
|
|
synthetic workloads have measured as high as 8%.
|
|
|
|
endmenu
|
|
|
|
endmenu
|