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compiler-based memory initialization
- Consolidate memory initialization Kconfigs (Kees) - Implement support for Clang's stack variable auto-init (Alexander) -----BEGIN PGP SIGNATURE----- Comment: Kees Cook <kees@outflux.net> iQJKBAABCgA0FiEEpcP2jyKd1g9yPm4TiXL039xtwCYFAlzQafUWHGtlZXNjb29r QGNocm9taXVtLm9yZwAKCRCJcvTf3G3AJrTfEAChweGM23u8i0vOgGM4fYAXr9di THoKkgEGgQJJaArgElEuZgwos8uhH2rGhQ2zcY38ZFA20byBZ/G8jFNXNuzFgUyQ 6p5DUU2P2qam+v/cXvFqBqbXg4VzmlwR6Lzi9DHZ3XC41kz5YUWqHTq3md1uCU82 V2Z0V3xF7Zvjx14V42UzEqW66l3dUrYPOFSJVTCMC5vaJvov3gFjStRkYuSzYg+N 1ns7SdT8sQvXeAoj1VSeunNuv8iCVytFWC6f0cIs3iCt9nD/IYk1d9Zl6MAqive2 5sKDhUKBzg03xB1rztDmxZKAyN3YYoZFfJr3PruSvUiMxYYtX3IMvKFI257RQl8J WYP5qa0kHHM1uel5kS4fckzAv+oqNnnXgdSy5ajc1YFcdBxwiy6DfvBjk843DyU/ +OLb1wh5Uz6ICg6GILgVoL5nZinnj73zgj78bfRemiy1j7LZVtkX0EDAwIJxE2U9 SYYeEvUu91jNbkE9ugu8RXmXv1QctOuiBr70VLupVu/a7AJij6Cq8Ox9uge25DRF XnuVjXCpMdx6p6i1kaNXZtxREK4at0J2CCIqGyzFpRgym2OpyJBIgVEWDMsfof0w HOKUpbp7TytVdRoEWcwU32oGBa/e0PbJ2KSNK0t+5bKeIOTxFJf1qeWwaWXu3JQE DRYx7/sVHjGUXsSNeg== =i0Gi -----END PGP SIGNATURE----- Merge tag 'meminit-v5.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux Pull compiler-based variable initialization updates from Kees Cook: "This is effectively part of my gcc-plugins tree, but as this adds some Clang support, it felt weird to still call it "gcc-plugins". :) This consolidates Kconfig for the existing stack variable initialization (via structleak and stackleak gcc plugins) and adds Alexander Potapenko's support for Clang's new similar functionality. Summary: - Consolidate memory initialization Kconfigs (Kees) - Implement support for Clang's stack variable auto-init (Alexander)" * tag 'meminit-v5.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: security: Implement Clang's stack initialization security: Move stackleak config to Kconfig.hardening security: Create "kernel hardening" config area
This commit is contained in:
Linus Torvalds
commit
2d60d96b6f
5
Makefile
5
Makefile
@ -748,6 +748,11 @@ KBUILD_CFLAGS += -fomit-frame-pointer
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endif
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endif
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# Initialize all stack variables with a pattern, if desired.
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ifdef CONFIG_INIT_STACK_ALL
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KBUILD_CFLAGS += -ftrivial-auto-var-init=pattern
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endif
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DEBUG_CFLAGS := $(call cc-option, -fno-var-tracking-assignments)
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ifdef CONFIG_DEBUG_INFO
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@ -13,17 +13,19 @@ config HAVE_GCC_PLUGINS
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An arch should select this symbol if it supports building with
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GCC plugins.
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menuconfig GCC_PLUGINS
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bool "GCC plugins"
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config GCC_PLUGINS
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bool
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depends on HAVE_GCC_PLUGINS
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depends on PLUGIN_HOSTCC != ""
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default y
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help
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GCC plugins are loadable modules that provide extra features to the
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compiler. They are useful for runtime instrumentation and static analysis.
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See Documentation/gcc-plugins.txt for details.
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if GCC_PLUGINS
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menu "GCC plugins"
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depends on GCC_PLUGINS
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config GCC_PLUGIN_CYC_COMPLEXITY
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bool "Compute the cyclomatic complexity of a function" if EXPERT
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@ -66,71 +68,6 @@ config GCC_PLUGIN_LATENT_ENTROPY
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* https://grsecurity.net/
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* https://pax.grsecurity.net/
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config GCC_PLUGIN_STRUCTLEAK
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bool "Zero initialize stack variables"
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help
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While the kernel is built with warnings enabled for any missed
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stack variable initializations, this warning is silenced for
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anything passed by reference to another function, under the
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occasionally misguided assumption that the function will do
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the initialization. As this regularly leads to exploitable
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flaws, this plugin is available to identify and zero-initialize
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such variables, depending on the chosen level of coverage.
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This plugin was originally ported from grsecurity/PaX. More
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information at:
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* https://grsecurity.net/
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* https://pax.grsecurity.net/
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choice
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prompt "Coverage"
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depends on GCC_PLUGIN_STRUCTLEAK
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default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
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help
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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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zero-initialized before use.
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config GCC_PLUGIN_STRUCTLEAK_USER
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bool "structs marked for userspace"
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help
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Zero-initialize any structures on the stack containing
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a __user attribute. This can prevent some classes of
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uninitialized stack variable exploits and information
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exposures, like CVE-2013-2141:
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https://git.kernel.org/linus/b9e146d8eb3b9eca
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config GCC_PLUGIN_STRUCTLEAK_BYREF
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bool "structs passed by reference"
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help
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Zero-initialize any structures on the stack that may
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be passed by reference and had not already been
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explicitly initialized. This can prevent most classes
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of uninitialized stack variable exploits and information
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exposures, like CVE-2017-1000410:
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https://git.kernel.org/linus/06e7e776ca4d3654
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config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
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bool "anything passed by reference"
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help
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Zero-initialize any stack variables that may be passed
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by reference and had not already been explicitly
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initialized. This is intended to eliminate all classes
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of uninitialized stack variable exploits and information
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exposures.
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endchoice
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config GCC_PLUGIN_STRUCTLEAK_VERBOSE
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bool "Report forcefully initialized variables"
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depends on GCC_PLUGIN_STRUCTLEAK
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depends on !COMPILE_TEST # too noisy
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help
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This option will cause a warning to be printed each time the
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structleak plugin finds a variable it thinks needs to be
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initialized. Since not all existing initializers are detected
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by the plugin, this can produce false positive warnings.
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config GCC_PLUGIN_RANDSTRUCT
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bool "Randomize layout of sensitive kernel structures"
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select MODVERSIONS if MODULES
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@ -171,59 +108,8 @@ config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE
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in structures. This reduces the performance hit of RANDSTRUCT
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at the cost of weakened randomization.
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config GCC_PLUGIN_STACKLEAK
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bool "Erase the kernel stack before returning from syscalls"
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depends on GCC_PLUGINS
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depends on HAVE_ARCH_STACKLEAK
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help
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This option makes the kernel erase the kernel stack before
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returning from system calls. That reduces the information which
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kernel stack leak bugs can reveal and blocks some uninitialized
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stack variable attacks.
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The tradeoff is the performance impact: on a single CPU system kernel
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compilation sees a 1% slowdown, other systems and workloads may vary
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and you are advised to test this feature on your expected workload
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before deploying it.
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This plugin was ported from grsecurity/PaX. More information at:
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* https://grsecurity.net/
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* https://pax.grsecurity.net/
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config STACKLEAK_TRACK_MIN_SIZE
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int "Minimum stack frame size of functions tracked by STACKLEAK"
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default 100
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range 0 4096
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depends on GCC_PLUGIN_STACKLEAK
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help
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The STACKLEAK gcc plugin instruments the kernel code for tracking
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the lowest border of the kernel stack (and for some other purposes).
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It inserts the stackleak_track_stack() call for the functions with
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a stack frame size greater than or equal to this parameter.
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If unsure, leave the default value 100.
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config STACKLEAK_METRICS
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bool "Show STACKLEAK metrics in the /proc file system"
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depends on GCC_PLUGIN_STACKLEAK
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depends on PROC_FS
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help
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If this is set, STACKLEAK metrics for every task are available in
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the /proc file system. In particular, /proc/<pid>/stack_depth
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shows the maximum kernel stack consumption for the current and
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previous syscalls. Although this information is not precise, it
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can be useful for estimating the STACKLEAK performance impact for
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your workloads.
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config STACKLEAK_RUNTIME_DISABLE
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bool "Allow runtime disabling of kernel stack erasing"
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depends on GCC_PLUGIN_STACKLEAK
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help
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This option provides 'stack_erasing' sysctl, which can be used in
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runtime to control kernel stack erasing for kernels built with
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CONFIG_GCC_PLUGIN_STACKLEAK.
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config GCC_PLUGIN_ARM_SSP_PER_TASK
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bool
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depends on GCC_PLUGINS && ARM
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endif
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endmenu
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@ -287,5 +287,7 @@ config LSM
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If unsure, leave this as the default.
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source "security/Kconfig.hardening"
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endmenu
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164
security/Kconfig.hardening
Normal file
164
security/Kconfig.hardening
Normal file
@ -0,0 +1,164 @@
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menu "Kernel hardening options"
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config GCC_PLUGIN_STRUCTLEAK
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bool
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help
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While the kernel is built with warnings enabled for any missed
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stack variable initializations, this warning is silenced for
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anything passed by reference to another function, under the
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occasionally misguided assumption that the function will do
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the initialization. As this regularly leads to exploitable
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flaws, this plugin is available to identify and zero-initialize
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such variables, depending on the chosen level of coverage.
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This plugin was originally ported from grsecurity/PaX. More
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information at:
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* https://grsecurity.net/
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* https://pax.grsecurity.net/
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menu "Memory initialization"
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config CC_HAS_AUTO_VAR_INIT
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def_bool $(cc-option,-ftrivial-auto-var-init=pattern)
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choice
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prompt "Initialize kernel stack variables at function entry"
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default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL if COMPILE_TEST && GCC_PLUGINS
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default INIT_STACK_ALL if COMPILE_TEST && CC_HAS_AUTO_VAR_INIT
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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 GCC_PLUGIN_STRUCTLEAK_USER
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bool "zero-init structs marked for userspace (weak)"
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depends on GCC_PLUGINS
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select GCC_PLUGIN_STRUCTLEAK
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help
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Zero-initialize any structures on the stack containing
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a __user attribute. This can prevent some classes of
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uninitialized stack variable exploits and information
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exposures, like CVE-2013-2141:
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https://git.kernel.org/linus/b9e146d8eb3b9eca
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config GCC_PLUGIN_STRUCTLEAK_BYREF
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bool "zero-init structs passed by reference (strong)"
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depends on GCC_PLUGINS
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select GCC_PLUGIN_STRUCTLEAK
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help
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Zero-initialize any structures on the stack that may
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be passed by reference and had not already been
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explicitly initialized. This can prevent most classes
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of uninitialized stack variable exploits and information
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exposures, like CVE-2017-1000410:
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https://git.kernel.org/linus/06e7e776ca4d3654
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config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
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bool "zero-init anything passed by reference (very strong)"
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depends on GCC_PLUGINS
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select GCC_PLUGIN_STRUCTLEAK
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help
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Zero-initialize any stack variables that may be passed
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by reference and had not already been explicitly
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initialized. This is intended to eliminate all classes
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of uninitialized stack variable exploits and information
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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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depends on CC_HAS_AUTO_VAR_INIT
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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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config GCC_PLUGIN_STRUCTLEAK_VERBOSE
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bool "Report forcefully initialized variables"
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depends on GCC_PLUGIN_STRUCTLEAK
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depends on !COMPILE_TEST # too noisy
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help
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This option will cause a warning to be printed each time the
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structleak plugin finds a variable it thinks needs to be
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initialized. Since not all existing initializers are detected
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by the plugin, this can produce false positive warnings.
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config GCC_PLUGIN_STACKLEAK
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bool "Poison kernel stack before returning from syscalls"
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depends on GCC_PLUGINS
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depends on HAVE_ARCH_STACKLEAK
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help
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This option makes the kernel erase the kernel stack before
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returning from system calls. This has the effect of leaving
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the stack initialized to the poison value, which both reduces
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the lifetime of any sensitive stack contents and reduces
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potential for uninitialized stack variable exploits or information
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exposures (it does not cover functions reaching the same stack
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depth as prior functions during the same syscall). This blocks
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most uninitialized stack variable attacks, with the performance
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impact being driven by the depth of the stack usage, rather than
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the function calling complexity.
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The performance impact on a single CPU system kernel compilation
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sees a 1% slowdown, other systems and workloads may vary and you
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are advised to test this feature on your expected workload before
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deploying it.
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|
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This plugin was ported from grsecurity/PaX. More information at:
|
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* https://grsecurity.net/
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* https://pax.grsecurity.net/
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config STACKLEAK_TRACK_MIN_SIZE
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int "Minimum stack frame size of functions tracked by STACKLEAK"
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default 100
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range 0 4096
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depends on GCC_PLUGIN_STACKLEAK
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help
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The STACKLEAK gcc plugin instruments the kernel code for tracking
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the lowest border of the kernel stack (and for some other purposes).
|
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It inserts the stackleak_track_stack() call for the functions with
|
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a stack frame size greater than or equal to this parameter.
|
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If unsure, leave the default value 100.
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config STACKLEAK_METRICS
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bool "Show STACKLEAK metrics in the /proc file system"
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depends on GCC_PLUGIN_STACKLEAK
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depends on PROC_FS
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help
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If this is set, STACKLEAK metrics for every task are available in
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the /proc file system. In particular, /proc/<pid>/stack_depth
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shows the maximum kernel stack consumption for the current and
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previous syscalls. Although this information is not precise, it
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can be useful for estimating the STACKLEAK performance impact for
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your workloads.
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|
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config STACKLEAK_RUNTIME_DISABLE
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bool "Allow runtime disabling of kernel stack erasing"
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depends on GCC_PLUGIN_STACKLEAK
|
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help
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This option provides 'stack_erasing' sysctl, which can be used in
|
||||
runtime to control kernel stack erasing for kernels built with
|
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CONFIG_GCC_PLUGIN_STACKLEAK.
|
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||||
endmenu
|
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endmenu
|
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