[thirdparty/linux.git] / security / Kconfig.hardening

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_USER
		bool "zero-init structs marked for userspace (weak)"
		depends on GCC_PLUGINS
		select GCC_PLUGIN_STRUCTLEAK
		help
		  Zero-initialize any structures on the stack containing
		  a __user attribute. This can prevent some classes of
		  uninitialized stack variable exploits and information
		  exposures, like CVE-2013-2141:
		  https://git.kernel.org/linus/b9e146d8eb3b9eca

	config GCC_PLUGIN_STRUCTLEAK_BYREF
		bool "zero-init structs passed by reference (strong)"
		depends on GCC_PLUGINS
		select GCC_PLUGIN_STRUCTLEAK
		help
		  Zero-initialize any structures on the stack that may
		  be passed by reference and had not already been
		  explicitly initialized. This can prevent most classes
		  of uninitialized stack variable exploits and information
		  exposures, like CVE-2017-1000410:
		  https://git.kernel.org/linus/06e7e776ca4d3654

	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 GCC_PLUGIN_STACKLEAK
	bool "Poison kernel stack before returning from syscalls"
	depends on GCC_PLUGINS
	depends on HAVE_ARCH_STACKLEAK
	help
	  This option makes the kernel erase the kernel stack before
	  returning from system calls. This has the effect of leaving
	  the stack initialized to the poison value, which both reduces
	  the lifetime of any sensitive stack contents and reduces
	  potential for uninitialized stack variable exploits or information
	  exposures (it does not cover functions reaching the same stack
	  depth as prior functions during the same syscall). This blocks
	  most uninitialized stack variable attacks, with the performance
	  impact being driven by the depth of the stack usage, rather than
	  the function calling complexity.

	  The performance impact on a single CPU system kernel compilation
	  sees a 1% slowdown, other systems and workloads may vary and you
	  are advised to test this feature on your expected workload before
	  deploying it.

	  This plugin was ported from grsecurity/PaX. More information at:
	   * https://grsecurity.net/
	   * https://pax.grsecurity.net/

config STACKLEAK_TRACK_MIN_SIZE
	int "Minimum stack frame size of functions tracked by STACKLEAK"
	default 100
	range 0 4096
	depends on GCC_PLUGIN_STACKLEAK
	help
	  The STACKLEAK gcc plugin instruments the kernel code for tracking
	  the lowest border of the kernel stack (and for some other purposes).
	  It inserts the stackleak_track_stack() call for the functions with
	  a stack frame size greater than or equal to this parameter.
	  If unsure, leave the default value 100.

config STACKLEAK_METRICS
	bool "Show STACKLEAK metrics in the /proc file system"
	depends on GCC_PLUGIN_STACKLEAK
	depends on PROC_FS
	help
	  If this is set, STACKLEAK metrics for every task are available in
	  the /proc file system. In particular, /proc/<pid>/stack_depth
	  shows the maximum kernel stack consumption for the current and
	  previous syscalls. Although this information is not precise, it
	  can be useful for estimating the STACKLEAK performance impact for
	  your workloads.

config STACKLEAK_RUNTIME_DISABLE
	bool "Allow runtime disabling of kernel stack erasing"
	depends on GCC_PLUGIN_STACKLEAK
	help
	  This option provides 'stack_erasing' sysctl, which can be used in
	  runtime to control kernel stack erasing for kernels built with
	  CONFIG_GCC_PLUGIN_STACKLEAK.

endmenu

endmenu
Commit	Line	Data
9f671e58 KC	1	menu "Kernel hardening options"
	2
	3	config GCC_PLUGIN_STRUCTLEAK
	4	bool
	5	help
	6	While the kernel is built with warnings enabled for any missed
	7	stack variable initializations, this warning is silenced for
	8	anything passed by reference to another function, under the
	9	occasionally misguided assumption that the function will do
	10	the initialization. As this regularly leads to exploitable
	11	flaws, this plugin is available to identify and zero-initialize
	12	such variables, depending on the chosen level of coverage.
	13
	14	This plugin was originally ported from grsecurity/PaX. More
	15	information at:
	16	* https://grsecurity.net/
	17	* https://pax.grsecurity.net/
	18
	19	menu "Memory initialization"
	20
709a972e KC	21	config CC_HAS_AUTO_VAR_INIT
	22	def_bool $(cc-option,-ftrivial-auto-var-init=pattern)
	23
9f671e58 KC	24	choice
	25	prompt "Initialize kernel stack variables at function entry"
	26	default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL if COMPILE_TEST && GCC_PLUGINS
709a972e	27	default INIT_STACK_ALL if COMPILE_TEST && CC_HAS_AUTO_VAR_INIT
9f671e58 KC	28	default INIT_STACK_NONE
	29	help
	30	This option enables initialization of stack variables at
	31	function entry time. This has the possibility to have the
	32	greatest coverage (since all functions can have their
	33	variables initialized), but the performance impact depends
	34	on the function calling complexity of a given workload's
	35	syscalls.
	36
	37	This chooses the level of coverage over classes of potentially
	38	uninitialized variables. The selected class will be
	39	initialized before use in a function.
	40
	41	config INIT_STACK_NONE
	42	bool "no automatic initialization (weakest)"
	43	help
	44	Disable automatic stack variable initialization.
	45	This leaves the kernel vulnerable to the standard
	46	classes of uninitialized stack variable exploits
	47	and information exposures.
	48
	49	config GCC_PLUGIN_STRUCTLEAK_USER
	50	bool "zero-init structs marked for userspace (weak)"
	51	depends on GCC_PLUGINS
	52	select GCC_PLUGIN_STRUCTLEAK
	53	help
	54	Zero-initialize any structures on the stack containing
	55	a __user attribute. This can prevent some classes of
	56	uninitialized stack variable exploits and information
	57	exposures, like CVE-2013-2141:
	58	https://git.kernel.org/linus/b9e146d8eb3b9eca
	59
	60	config GCC_PLUGIN_STRUCTLEAK_BYREF
	61	bool "zero-init structs passed by reference (strong)"
	62	depends on GCC_PLUGINS
	63	select GCC_PLUGIN_STRUCTLEAK
	64	help
	65	Zero-initialize any structures on the stack that may
	66	be passed by reference and had not already been
	67	explicitly initialized. This can prevent most classes
	68	of uninitialized stack variable exploits and information
	69	exposures, like CVE-2017-1000410:
	70	https://git.kernel.org/linus/06e7e776ca4d3654
	71
	72	config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
	73	bool "zero-init anything passed by reference (very strong)"
	74	depends on GCC_PLUGINS
	75	select GCC_PLUGIN_STRUCTLEAK
	76	help
	77	Zero-initialize any stack variables that may be passed
	78	by reference and had not already been explicitly
	79	initialized. This is intended to eliminate all classes
	80	of uninitialized stack variable exploits and information
	81	exposures.
	82
709a972e KC	83	config INIT_STACK_ALL
	84	bool "0xAA-init everything on the stack (strongest)"
	85	depends on CC_HAS_AUTO_VAR_INIT
	86	help
	87	Initializes everything on the stack with a 0xAA
	88	pattern. This is intended to eliminate all classes
	89	of uninitialized stack variable exploits and information
	90	exposures, even variables that were warned to have been
	91	left uninitialized.
	92
9f671e58 KC	93	endchoice
	94
	95	config GCC_PLUGIN_STRUCTLEAK_VERBOSE
	96	bool "Report forcefully initialized variables"
	97	depends on GCC_PLUGIN_STRUCTLEAK
	98	depends on !COMPILE_TEST # too noisy
	99	help
	100	This option will cause a warning to be printed each time the
	101	structleak plugin finds a variable it thinks needs to be
	102	initialized. Since not all existing initializers are detected
	103	by the plugin, this can produce false positive warnings.
	104
b6a6a377 KC	105	config GCC_PLUGIN_STACKLEAK
	106	bool "Poison kernel stack before returning from syscalls"
	107	depends on GCC_PLUGINS
	108	depends on HAVE_ARCH_STACKLEAK
	109	help
	110	This option makes the kernel erase the kernel stack before
	111	returning from system calls. This has the effect of leaving
	112	the stack initialized to the poison value, which both reduces
	113	the lifetime of any sensitive stack contents and reduces
	114	potential for uninitialized stack variable exploits or information
	115	exposures (it does not cover functions reaching the same stack
	116	depth as prior functions during the same syscall). This blocks
	117	most uninitialized stack variable attacks, with the performance
	118	impact being driven by the depth of the stack usage, rather than
	119	the function calling complexity.
	120
	121	The performance impact on a single CPU system kernel compilation
	122	sees a 1% slowdown, other systems and workloads may vary and you
	123	are advised to test this feature on your expected workload before
	124	deploying it.
	125
	126	This plugin was ported from grsecurity/PaX. More information at:
	127	* https://grsecurity.net/
	128	* https://pax.grsecurity.net/
	129
	130	config STACKLEAK_TRACK_MIN_SIZE
	131	int "Minimum stack frame size of functions tracked by STACKLEAK"
	132	default 100
	133	range 0 4096
	134	depends on GCC_PLUGIN_STACKLEAK
	135	help
	136	The STACKLEAK gcc plugin instruments the kernel code for tracking
	137	the lowest border of the kernel stack (and for some other purposes).
	138	It inserts the stackleak_track_stack() call for the functions with
	139	a stack frame size greater than or equal to this parameter.
	140	If unsure, leave the default value 100.
	141
	142	config STACKLEAK_METRICS
	143	bool "Show STACKLEAK metrics in the /proc file system"
	144	depends on GCC_PLUGIN_STACKLEAK
	145	depends on PROC_FS
	146	help
	147	If this is set, STACKLEAK metrics for every task are available in
	148	the /proc file system. In particular, /proc/<pid>/stack_depth
	149	shows the maximum kernel stack consumption for the current and
	150	previous syscalls. Although this information is not precise, it
	151	can be useful for estimating the STACKLEAK performance impact for
	152	your workloads.
	153
	154	config STACKLEAK_RUNTIME_DISABLE
	155	bool "Allow runtime disabling of kernel stack erasing"
	156	depends on GCC_PLUGIN_STACKLEAK
	157	help
	158	This option provides 'stack_erasing' sysctl, which can be used in
	159	runtime to control kernel stack erasing for kernels built with
	160	CONFIG_GCC_PLUGIN_STACKLEAK.
	161
9f671e58 KC	162	endmenu
	163
	164	endmenu