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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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10e9ae9fab
The STACKLEAK feature erases the kernel stack before returning from syscalls. That reduces the information which kernel stack leak bugs can reveal and blocks some uninitialized stack variable attacks. This commit introduces the STACKLEAK gcc plugin. It is needed for tracking the lowest border of the kernel stack, which is important for the code erasing the used part of the kernel stack at the end of syscalls (comes in a separate commit). The STACKLEAK feature is ported from grsecurity/PaX. More information at: https://grsecurity.net/ https://pax.grsecurity.net/ This code is modified from Brad Spengler/PaX Team's code in the last public patch of grsecurity/PaX based on our understanding of the code. Changes or omissions from the original code are ours and don't reflect the original grsecurity/PaX code. Signed-off-by: Alexander Popov <alex.popov@linux.com> Tested-by: Laura Abbott <labbott@redhat.com> Signed-off-by: Kees Cook <keescook@chromium.org>
173 lines
6.4 KiB
Text
173 lines
6.4 KiB
Text
preferred-plugin-hostcc := $(if-success,[ $(gcc-version) -ge 40800 ],$(HOSTCXX),$(HOSTCC))
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config PLUGIN_HOSTCC
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string
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default "$(shell,$(srctree)/scripts/gcc-plugin.sh "$(preferred-plugin-hostcc)" "$(HOSTCXX)" "$(CC)")" if CC_IS_GCC
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help
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Host compiler used to build GCC plugins. This can be $(HOSTCXX),
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$(HOSTCC), or a null string if GCC plugin is unsupported.
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config HAVE_GCC_PLUGINS
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bool
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help
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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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depends on HAVE_GCC_PLUGINS
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depends on PLUGIN_HOSTCC != ""
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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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config GCC_PLUGIN_CYC_COMPLEXITY
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bool "Compute the cyclomatic complexity of a function" if EXPERT
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depends on !COMPILE_TEST # too noisy
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help
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The complexity M of a function's control flow graph is defined as:
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M = E - N + 2P
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where
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E = the number of edges
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N = the number of nodes
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P = the number of connected components (exit nodes).
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Enabling this plugin reports the complexity to stderr during the
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build. It mainly serves as a simple example of how to create a
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gcc plugin for the kernel.
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config GCC_PLUGIN_SANCOV
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bool
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help
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This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
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basic blocks. It supports all gcc versions with plugin support (from
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gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
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by Dmitry Vyukov <dvyukov@google.com>.
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config GCC_PLUGIN_LATENT_ENTROPY
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bool "Generate some entropy during boot and runtime"
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help
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By saying Y here the kernel will instrument some kernel code to
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extract some entropy from both original and artificially created
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program state. This will help especially embedded systems where
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there is little 'natural' source of entropy normally. The cost
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is some slowdown of the boot process (about 0.5%) and fork and
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irq processing.
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Note that entropy extracted this way is not cryptographically
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secure!
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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 GCC_PLUGIN_STRUCTLEAK
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bool "Force initialization of variables containing userspace addresses"
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# Currently STRUCTLEAK inserts initialization out of live scope of
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# variables from KASAN point of view. This leads to KASAN false
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# positive reports. Prohibit this combination for now.
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depends on !KASAN_EXTRA
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help
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This plugin zero-initializes any structures containing a
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__user attribute. This can prevent some classes of information
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exposures.
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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 GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
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bool "Force initialize all struct type variables passed by reference"
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depends on GCC_PLUGIN_STRUCTLEAK
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depends on !COMPILE_TEST
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help
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Zero initialize any struct type local variable that may be passed by
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reference without having been initialized.
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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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help
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If you say Y here, the layouts of structures that are entirely
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function pointers (and have not been manually annotated with
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__no_randomize_layout), or structures that have been explicitly
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marked with __randomize_layout, will be randomized at compile-time.
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This can introduce the requirement of an additional information
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exposure vulnerability for exploits targeting these structure
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types.
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Enabling this feature will introduce some performance impact,
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slightly increase memory usage, and prevent the use of forensic
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tools like Volatility against the system (unless the kernel
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source tree isn't cleaned after kernel installation).
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The seed used for compilation is located at
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scripts/gcc-plgins/randomize_layout_seed.h. It remains after
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a make clean to allow for external modules to be compiled with
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the existing seed and will be removed by a make mrproper or
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make distclean.
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Note that the implementation requires gcc 4.7 or newer.
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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 GCC_PLUGIN_RANDSTRUCT_PERFORMANCE
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bool "Use cacheline-aware structure randomization"
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depends on GCC_PLUGIN_RANDSTRUCT
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depends on !COMPILE_TEST # do not reduce test coverage
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help
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If you say Y here, the RANDSTRUCT randomization will make a
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best effort at restricting randomization to cacheline-sized
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groups of elements. It will further not randomize bitfields
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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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endif
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