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5bb098df6f
CONFIG_INIT_STACK_ALL turns on stack initialization based on
-ftrivial-auto-var-init in Clang builds, which has greater coverage
than CONFIG_GCC_PLUGINS_STRUCTLEAK_BYREF_ALL.
-ftrivial-auto-var-init Clang option provides trivial initializers for
uninitialized local variables, variable fields and padding.
It has three possible values:
pattern - uninitialized locals are filled with a fixed pattern
(mostly 0xAA on 64-bit platforms, see https://reviews.llvm.org/D54604
for more details, but 0x000000AA for 32-bit pointers) likely to cause
crashes when uninitialized value is used;
zero (it's still debated whether this flag makes it to the official
Clang release) - uninitialized locals are filled with zeroes;
uninitialized (default) - uninitialized locals are left intact.
This patch uses only the "pattern" mode when CONFIG_INIT_STACK_ALL is
enabled.
Developers have the possibility to opt-out of this feature on a
per-variable basis by using __attribute__((uninitialized)), but such
use should be well justified in comments.
The Android 4.14 backport drops CC_HAS_AUTO_VAR_INIT, because Kconfig
is too old to support compiler feature checks.
Change-Id: I8e990ac3f299be9f6658a881a0518290cdda1157
Co-developed-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Tested-by: Alexander Potapenko <glider@google.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
(cherry picked from commit 709a972efb01efaeb97cad1adc87fe400119c8ab)
Bug: 133428616
Signed-off-by: Alexander Potapenko <glider@google.com>
42 lines
1.2 KiB
Plaintext
42 lines
1.2 KiB
Plaintext
menu "Kernel hardening options"
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menu "Memory initialization"
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choice
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prompt "Initialize kernel stack variables at function entry"
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default INIT_STACK_NONE
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help
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This option enables initialization of stack variables at
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function entry time. This has the possibility to have the
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greatest coverage (since all functions can have their
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variables initialized), but the performance impact depends
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on the function calling complexity of a given workload's
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syscalls.
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This chooses the level of coverage over classes of potentially
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uninitialized variables. The selected class will be
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initialized before use in a function.
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config INIT_STACK_NONE
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bool "no automatic initialization (weakest)"
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help
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Disable automatic stack variable initialization.
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This leaves the kernel vulnerable to the standard
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classes of uninitialized stack variable exploits
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and information exposures.
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config INIT_STACK_ALL
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bool "0xAA-init everything on the stack (strongest)"
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help
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Initializes everything on the stack with a 0xAA
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pattern. This is intended to eliminate all classes
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of uninitialized stack variable exploits and information
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exposures, even variables that were warned to have been
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left uninitialized.
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endchoice
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endmenu
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endmenu
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