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

Linus Torvalds committed 7 years ago

Commit 2d60d962 parents eac7078 709a9724 files · +177 −120Browse files

Unified · Split

4 files

Makefile +5 −0
scripts/gcc-plugins/Kconfig +6 −120
security/Kconfig +2 −0
security/Kconfig.hardening +164 −0

Makefile+5−0

@@ -748,6 +748,11 @@ KBUILD_CFLAGS += -fomit-frame-pointer · 747 unmodified lines
748	748	endif
749	749	endif
750	750
	751	+# Initialize all stack variables with a pattern, if desired.
	752	+ifdef CONFIG_INIT_STACK_ALL
	753	+KBUILD_CFLAGS += -ftrivial-auto-var-init=pattern
	754	+endif
	755	+
751	756	DEBUG_CFLAGS := $(call cc-option, -fno-var-tracking-assignments)
752	757
753	758	ifdef CONFIG_DEBUG_INFO

scripts/gcc-plugins/Kconfig+6−120

@@ -13,17 +13,19 @@ config HAVE_GCC_PLUGINS · 12 unmodified lines
13	13	An arch should select this symbol if it supports building with
14	14	GCC plugins.
15	15
16		−menuconfig GCC_PLUGINS
17		− bool "GCC plugins"
	16	+config GCC_PLUGINS
	17	+ bool
18	18	depends on HAVE_GCC_PLUGINS
19	19	depends on PLUGIN_HOSTCC != ""
	20	+ default y
20	21	help
21	22	GCC plugins are loadable modules that provide extra features to the
22	23	compiler. They are useful for runtime instrumentation and static analysis.
23	24
24	25	See Documentation/gcc-plugins.txt for details.
25	26
26		−if GCC_PLUGINS
	27	+menu "GCC plugins"
	28	+ depends on GCC_PLUGINS
27	29
28	30	config GCC_PLUGIN_CYC_COMPLEXITY
29	31	bool "Compute the cyclomatic complexity of a function" if EXPERT
@@ -66,71 +68,6 @@ config GCC_PLUGIN_LATENT_ENTROPY · 36 unmodified lines
66	68	* https://grsecurity.net/
67	69	* https://pax.grsecurity.net/
68	70
69		−config GCC_PLUGIN_STRUCTLEAK
70		− bool "Zero initialize stack variables"
71		− help
72		− While the kernel is built with warnings enabled for any missed
73		− stack variable initializations, this warning is silenced for
74		− anything passed by reference to another function, under the
75		− occasionally misguided assumption that the function will do
76		− the initialization. As this regularly leads to exploitable
77		− flaws, this plugin is available to identify and zero-initialize
78		− such variables, depending on the chosen level of coverage.
79		−
80		− This plugin was originally ported from grsecurity/PaX. More
81		− information at:
82		− * https://grsecurity.net/
83		− * https://pax.grsecurity.net/
84		−
85		−choice
86		− prompt "Coverage"
87		− depends on GCC_PLUGIN_STRUCTLEAK
88		− default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
89		− help
90		− This chooses the level of coverage over classes of potentially
91		− uninitialized variables. The selected class will be
92		− zero-initialized before use.
93		−
94		− config GCC_PLUGIN_STRUCTLEAK_USER
95		− bool "structs marked for userspace"
96		− help
97		− Zero-initialize any structures on the stack containing
98		− a __user attribute. This can prevent some classes of
99		− uninitialized stack variable exploits and information
100		− exposures, like CVE-2013-2141:
101		− https://git.kernel.org/linus/b9e146d8eb3b9eca
102		−
103		− config GCC_PLUGIN_STRUCTLEAK_BYREF
104		− bool "structs passed by reference"
105		− help
106		− Zero-initialize any structures on the stack that may
107		− be passed by reference and had not already been
108		− explicitly initialized. This can prevent most classes
109		− of uninitialized stack variable exploits and information
110		− exposures, like CVE-2017-1000410:
111		− https://git.kernel.org/linus/06e7e776ca4d3654
112		−
113		− config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
114		− bool "anything passed by reference"
115		− help
116		− Zero-initialize any stack variables that may be passed
117		− by reference and had not already been explicitly
118		− initialized. This is intended to eliminate all classes
119		− of uninitialized stack variable exploits and information
120		− exposures.
121		−
122		−endchoice
123		−
124		−config GCC_PLUGIN_STRUCTLEAK_VERBOSE
125		− bool "Report forcefully initialized variables"
126		− depends on GCC_PLUGIN_STRUCTLEAK
127		− depends on !COMPILE_TEST # too noisy
128		− help
129		− This option will cause a warning to be printed each time the
130		− structleak plugin finds a variable it thinks needs to be
131		− initialized. Since not all existing initializers are detected
132		− by the plugin, this can produce false positive warnings.
133		−
134	71	config GCC_PLUGIN_RANDSTRUCT
135	72	bool "Randomize layout of sensitive kernel structures"
136	73	select MODVERSIONS if MODULES
@@ -171,59 +108,8 @@ config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE · 34 unmodified lines
171	108	in structures. This reduces the performance hit of RANDSTRUCT
172	109	at the cost of weakened randomization.
173	110
174		−config GCC_PLUGIN_STACKLEAK
175		− bool "Erase the kernel stack before returning from syscalls"
176		− depends on GCC_PLUGINS
177		− depends on HAVE_ARCH_STACKLEAK
178		− help
179		− This option makes the kernel erase the kernel stack before
180		− returning from system calls. That reduces the information which
181		− kernel stack leak bugs can reveal and blocks some uninitialized
182		− stack variable attacks.
183		−
184		− The tradeoff is the performance impact: on a single CPU system kernel
185		− compilation sees a 1% slowdown, other systems and workloads may vary
186		− and you are advised to test this feature on your expected workload
187		− before deploying it.
188		−
189		− This plugin was ported from grsecurity/PaX. More information at:
190		− * https://grsecurity.net/
191		− * https://pax.grsecurity.net/
192		−
193		−config STACKLEAK_TRACK_MIN_SIZE
194		− int "Minimum stack frame size of functions tracked by STACKLEAK"
195		− default 100
196		− range 0 4096
197		− depends on GCC_PLUGIN_STACKLEAK
198		− help
199		− The STACKLEAK gcc plugin instruments the kernel code for tracking
200		− the lowest border of the kernel stack (and for some other purposes).
201		− It inserts the stackleak_track_stack() call for the functions with
202		− a stack frame size greater than or equal to this parameter.
203		− If unsure, leave the default value 100.
204		−
205		−config STACKLEAK_METRICS
206		− bool "Show STACKLEAK metrics in the /proc file system"
207		− depends on GCC_PLUGIN_STACKLEAK
208		− depends on PROC_FS
209		− help
210		− If this is set, STACKLEAK metrics for every task are available in
211		− the /proc file system. In particular, /proc/<pid>/stack_depth
212		− shows the maximum kernel stack consumption for the current and
213		− previous syscalls. Although this information is not precise, it
214		− can be useful for estimating the STACKLEAK performance impact for
215		− your workloads.
216		−
217		−config STACKLEAK_RUNTIME_DISABLE
218		− bool "Allow runtime disabling of kernel stack erasing"
219		− depends on GCC_PLUGIN_STACKLEAK
220		− help
221		− This option provides 'stack_erasing' sysctl, which can be used in
222		− runtime to control kernel stack erasing for kernels built with
223		− CONFIG_GCC_PLUGIN_STACKLEAK.
224		−
225	111	config GCC_PLUGIN_ARM_SSP_PER_TASK
226	112	bool
227	113	depends on GCC_PLUGINS && ARM
228	114
229		−endif
	115	+endmenu

security/Kconfig+2−0

@@ -287,5 +287,7 @@ config LSM · 286 unmodified lines
287	287
288	288	If unsure, leave this as the default.
289	289
	290	+source "security/Kconfig.hardening"
	291	+
290	292	endmenu
291	293

security/Kconfig.hardening+164−0

@@ -0,0 +1,164 @@
	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	+
	21	+config CC_HAS_AUTO_VAR_INIT
	22	+ def_bool $(cc-option,-ftrivial-auto-var-init=pattern)
	23	+
	24	+choice
	25	+ prompt "Initialize kernel stack variables at function entry"
	26	+ default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL if COMPILE_TEST && GCC_PLUGINS
	27	+ default INIT_STACK_ALL if COMPILE_TEST && CC_HAS_AUTO_VAR_INIT
	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	+
	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	+
	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	+
	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	+
	162	+endmenu
	163	+
	164	+endmenu