1 # SPDX-License-Identifier: GPL-2.0-only 1 # SPDX-License-Identifier: GPL-2.0-only
2 menu "Kernel hardening options" 2 menu "Kernel hardening options"
3 3
4 config GCC_PLUGIN_STRUCTLEAK 4 config GCC_PLUGIN_STRUCTLEAK
5 bool 5 bool
6 help 6 help
7 While the kernel is built with warni 7 While the kernel is built with warnings enabled for any missed
8 stack variable initializations, this 8 stack variable initializations, this warning is silenced for
9 anything passed by reference to anot 9 anything passed by reference to another function, under the
10 occasionally misguided assumption th 10 occasionally misguided assumption that the function will do
11 the initialization. As this regularl 11 the initialization. As this regularly leads to exploitable
12 flaws, this plugin is available to i 12 flaws, this plugin is available to identify and zero-initialize
13 such variables, depending on the cho 13 such variables, depending on the chosen level of coverage.
14 14
15 This plugin was originally ported fr 15 This plugin was originally ported from grsecurity/PaX. More
16 information at: 16 information at:
17 * https://grsecurity.net/ 17 * https://grsecurity.net/
18 * https://pax.grsecurity.net/ 18 * https://pax.grsecurity.net/
19 19
20 menu "Memory initialization" 20 menu "Memory initialization"
21 21
22 config CC_HAS_AUTO_VAR_INIT_PATTERN 22 config CC_HAS_AUTO_VAR_INIT_PATTERN
23 def_bool $(cc-option,-ftrivial-auto-va 23 def_bool $(cc-option,-ftrivial-auto-var-init=pattern)
24 24
25 config CC_HAS_AUTO_VAR_INIT_ZERO_BARE 25 config CC_HAS_AUTO_VAR_INIT_ZERO_BARE
26 def_bool $(cc-option,-ftrivial-auto-va 26 def_bool $(cc-option,-ftrivial-auto-var-init=zero)
27 27
28 config CC_HAS_AUTO_VAR_INIT_ZERO_ENABLER 28 config CC_HAS_AUTO_VAR_INIT_ZERO_ENABLER
29 # Clang 16 and later warn about using 29 # Clang 16 and later warn about using the -enable flag, but it
30 # is required before then. 30 # is required before then.
31 def_bool $(cc-option,-ftrivial-auto-va 31 def_bool $(cc-option,-ftrivial-auto-var-init=zero -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang)
32 depends on !CC_HAS_AUTO_VAR_INIT_ZERO_ 32 depends on !CC_HAS_AUTO_VAR_INIT_ZERO_BARE
33 33
34 config CC_HAS_AUTO_VAR_INIT_ZERO 34 config CC_HAS_AUTO_VAR_INIT_ZERO
35 def_bool CC_HAS_AUTO_VAR_INIT_ZERO_BAR 35 def_bool CC_HAS_AUTO_VAR_INIT_ZERO_BARE || CC_HAS_AUTO_VAR_INIT_ZERO_ENABLER
36 36
37 choice 37 choice
38 prompt "Initialize kernel stack variab 38 prompt "Initialize kernel stack variables at function entry"
39 default GCC_PLUGIN_STRUCTLEAK_BYREF_AL 39 default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL if COMPILE_TEST && GCC_PLUGINS
40 default INIT_STACK_ALL_PATTERN if COMP 40 default INIT_STACK_ALL_PATTERN if COMPILE_TEST && CC_HAS_AUTO_VAR_INIT_PATTERN
41 default INIT_STACK_ALL_ZERO if CC_HAS_ 41 default INIT_STACK_ALL_ZERO if CC_HAS_AUTO_VAR_INIT_ZERO
42 default INIT_STACK_NONE 42 default INIT_STACK_NONE
43 help 43 help
44 This option enables initialization o 44 This option enables initialization of stack variables at
45 function entry time. This has the po 45 function entry time. This has the possibility to have the
46 greatest coverage (since all functio 46 greatest coverage (since all functions can have their
47 variables initialized), but the perf 47 variables initialized), but the performance impact depends
48 on the function calling complexity o 48 on the function calling complexity of a given workload's
49 syscalls. 49 syscalls.
50 50
51 This chooses the level of coverage o 51 This chooses the level of coverage over classes of potentially
52 uninitialized variables. The selecte 52 uninitialized variables. The selected class of variable will be
53 initialized before use in a function 53 initialized before use in a function.
54 54
55 config INIT_STACK_NONE 55 config INIT_STACK_NONE
56 bool "no automatic stack varia 56 bool "no automatic stack variable initialization (weakest)"
57 help 57 help
58 Disable automatic stack vari 58 Disable automatic stack variable initialization.
59 This leaves the kernel vulne 59 This leaves the kernel vulnerable to the standard
60 classes of uninitialized sta 60 classes of uninitialized stack variable exploits
61 and information exposures. 61 and information exposures.
62 62
63 config GCC_PLUGIN_STRUCTLEAK_USER 63 config GCC_PLUGIN_STRUCTLEAK_USER
64 bool "zero-init structs marked 64 bool "zero-init structs marked for userspace (weak)"
65 # Plugin can be removed once t 65 # Plugin can be removed once the kernel only supports GCC 12+
66 depends on GCC_PLUGINS && !CC_ 66 depends on GCC_PLUGINS && !CC_HAS_AUTO_VAR_INIT_ZERO
67 select GCC_PLUGIN_STRUCTLEAK 67 select GCC_PLUGIN_STRUCTLEAK
68 help 68 help
69 Zero-initialize any structur 69 Zero-initialize any structures on the stack containing
70 a __user attribute. This can 70 a __user attribute. This can prevent some classes of
71 uninitialized stack variable 71 uninitialized stack variable exploits and information
72 exposures, like CVE-2013-214 72 exposures, like CVE-2013-2141:
73 https://git.kernel.org/linus 73 https://git.kernel.org/linus/b9e146d8eb3b9eca
74 74
75 config GCC_PLUGIN_STRUCTLEAK_BYREF 75 config GCC_PLUGIN_STRUCTLEAK_BYREF
76 bool "zero-init structs passed 76 bool "zero-init structs passed by reference (strong)"
77 # Plugin can be removed once t 77 # Plugin can be removed once the kernel only supports GCC 12+
78 depends on GCC_PLUGINS && !CC_ 78 depends on GCC_PLUGINS && !CC_HAS_AUTO_VAR_INIT_ZERO
79 depends on !(KASAN && KASAN_ST 79 depends on !(KASAN && KASAN_STACK)
80 select GCC_PLUGIN_STRUCTLEAK 80 select GCC_PLUGIN_STRUCTLEAK
81 help 81 help
82 Zero-initialize any structur 82 Zero-initialize any structures on the stack that may
83 be passed by reference and h 83 be passed by reference and had not already been
84 explicitly initialized. This 84 explicitly initialized. This can prevent most classes
85 of uninitialized stack varia 85 of uninitialized stack variable exploits and information
86 exposures, like CVE-2017-100 86 exposures, like CVE-2017-1000410:
87 https://git.kernel.org/linus 87 https://git.kernel.org/linus/06e7e776ca4d3654
88 88
89 As a side-effect, this keeps 89 As a side-effect, this keeps a lot of variables on the
90 stack that can otherwise be 90 stack that can otherwise be optimized out, so combining
91 this with CONFIG_KASAN_STACK 91 this with CONFIG_KASAN_STACK can lead to a stack overflow
92 and is disallowed. 92 and is disallowed.
93 93
94 config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL 94 config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
95 bool "zero-init everything pas 95 bool "zero-init everything passed by reference (very strong)"
96 # Plugin can be removed once t 96 # Plugin can be removed once the kernel only supports GCC 12+
97 depends on GCC_PLUGINS && !CC_ 97 depends on GCC_PLUGINS && !CC_HAS_AUTO_VAR_INIT_ZERO
98 depends on !(KASAN && KASAN_ST 98 depends on !(KASAN && KASAN_STACK)
99 select GCC_PLUGIN_STRUCTLEAK 99 select GCC_PLUGIN_STRUCTLEAK
100 help 100 help
101 Zero-initialize any stack va 101 Zero-initialize any stack variables that may be passed
102 by reference and had not alr 102 by reference and had not already been explicitly
103 initialized. This is intende 103 initialized. This is intended to eliminate all classes
104 of uninitialized stack varia 104 of uninitialized stack variable exploits and information
105 exposures. 105 exposures.
106 106
107 As a side-effect, this keeps 107 As a side-effect, this keeps a lot of variables on the
108 stack that can otherwise be 108 stack that can otherwise be optimized out, so combining
109 this with CONFIG_KASAN_STACK 109 this with CONFIG_KASAN_STACK can lead to a stack overflow
110 and is disallowed. 110 and is disallowed.
111 111
112 config INIT_STACK_ALL_PATTERN 112 config INIT_STACK_ALL_PATTERN
113 bool "pattern-init everything 113 bool "pattern-init everything (strongest)"
114 depends on CC_HAS_AUTO_VAR_INI 114 depends on CC_HAS_AUTO_VAR_INIT_PATTERN
115 depends on !KMSAN <<
116 help 115 help
117 Initializes everything on th 116 Initializes everything on the stack (including padding)
118 with a specific debug value. 117 with a specific debug value. This is intended to eliminate
119 all classes of uninitialized 118 all classes of uninitialized stack variable exploits and
120 information exposures, even 119 information exposures, even variables that were warned about
121 having been left uninitializ 120 having been left uninitialized.
122 121
123 Pattern initialization is kn 122 Pattern initialization is known to provoke many existing bugs
124 related to uninitialized loc 123 related to uninitialized locals, e.g. pointers receive
125 non-NULL values, buffer size 124 non-NULL values, buffer sizes and indices are very big. The
126 pattern is situation-specifi 125 pattern is situation-specific; Clang on 64-bit uses 0xAA
127 repeating for all types and 126 repeating for all types and padding except float and double
128 which use 0xFF repeating (-N 127 which use 0xFF repeating (-NaN). Clang on 32-bit uses 0xFF
129 repeating for all types and 128 repeating for all types and padding.
130 129
131 config INIT_STACK_ALL_ZERO 130 config INIT_STACK_ALL_ZERO
132 bool "zero-init everything (st 131 bool "zero-init everything (strongest and safest)"
133 depends on CC_HAS_AUTO_VAR_INI 132 depends on CC_HAS_AUTO_VAR_INIT_ZERO
134 depends on !KMSAN <<
135 help 133 help
136 Initializes everything on th 134 Initializes everything on the stack (including padding)
137 with a zero value. This is i 135 with a zero value. This is intended to eliminate all
138 classes of uninitialized sta 136 classes of uninitialized stack variable exploits and
139 information exposures, even 137 information exposures, even variables that were warned
140 about having been left unini 138 about having been left uninitialized.
141 139
142 Zero initialization provides 140 Zero initialization provides safe defaults for strings
143 (immediately NUL-terminated) 141 (immediately NUL-terminated), pointers (NULL), indices
144 (index 0), and sizes (0 leng 142 (index 0), and sizes (0 length), so it is therefore more
145 suitable as a production sec 143 suitable as a production security mitigation than pattern
146 initialization. 144 initialization.
147 145
148 endchoice 146 endchoice
149 147
150 config GCC_PLUGIN_STRUCTLEAK_VERBOSE 148 config GCC_PLUGIN_STRUCTLEAK_VERBOSE
151 bool "Report forcefully initialized va 149 bool "Report forcefully initialized variables"
152 depends on GCC_PLUGIN_STRUCTLEAK 150 depends on GCC_PLUGIN_STRUCTLEAK
153 depends on !COMPILE_TEST # too 151 depends on !COMPILE_TEST # too noisy
154 help 152 help
155 This option will cause a warning to 153 This option will cause a warning to be printed each time the
156 structleak plugin finds a variable i 154 structleak plugin finds a variable it thinks needs to be
157 initialized. Since not all existing 155 initialized. Since not all existing initializers are detected
158 by the plugin, this can produce fals 156 by the plugin, this can produce false positive warnings.
159 157
160 config GCC_PLUGIN_STACKLEAK 158 config GCC_PLUGIN_STACKLEAK
161 bool "Poison kernel stack before retur 159 bool "Poison kernel stack before returning from syscalls"
162 depends on GCC_PLUGINS 160 depends on GCC_PLUGINS
163 depends on HAVE_ARCH_STACKLEAK 161 depends on HAVE_ARCH_STACKLEAK
164 help 162 help
165 This option makes the kernel erase t 163 This option makes the kernel erase the kernel stack before
166 returning from system calls. This ha 164 returning from system calls. This has the effect of leaving
167 the stack initialized to the poison 165 the stack initialized to the poison value, which both reduces
168 the lifetime of any sensitive stack 166 the lifetime of any sensitive stack contents and reduces
169 potential for uninitialized stack va 167 potential for uninitialized stack variable exploits or information
170 exposures (it does not cover functio 168 exposures (it does not cover functions reaching the same stack
171 depth as prior functions during the 169 depth as prior functions during the same syscall). This blocks
172 most uninitialized stack variable at 170 most uninitialized stack variable attacks, with the performance
173 impact being driven by the depth of 171 impact being driven by the depth of the stack usage, rather than
174 the function calling complexity. 172 the function calling complexity.
175 173
176 The performance impact on a single C 174 The performance impact on a single CPU system kernel compilation
177 sees a 1% slowdown, other systems an 175 sees a 1% slowdown, other systems and workloads may vary and you
178 are advised to test this feature on 176 are advised to test this feature on your expected workload before
179 deploying it. 177 deploying it.
180 178
181 This plugin was ported from grsecuri 179 This plugin was ported from grsecurity/PaX. More information at:
182 * https://grsecurity.net/ 180 * https://grsecurity.net/
183 * https://pax.grsecurity.net/ 181 * https://pax.grsecurity.net/
184 182
185 config GCC_PLUGIN_STACKLEAK_VERBOSE 183 config GCC_PLUGIN_STACKLEAK_VERBOSE
186 bool "Report stack depth analysis inst 184 bool "Report stack depth analysis instrumentation" if EXPERT
187 depends on GCC_PLUGIN_STACKLEAK 185 depends on GCC_PLUGIN_STACKLEAK
188 depends on !COMPILE_TEST # too 186 depends on !COMPILE_TEST # too noisy
189 help 187 help
190 This option will cause a warning to 188 This option will cause a warning to be printed each time the
191 stackleak plugin finds a function it 189 stackleak plugin finds a function it thinks needs to be
192 instrumented. This is useful for com 190 instrumented. This is useful for comparing coverage between
193 builds. 191 builds.
194 192
195 config STACKLEAK_TRACK_MIN_SIZE 193 config STACKLEAK_TRACK_MIN_SIZE
196 int "Minimum stack frame size of funct 194 int "Minimum stack frame size of functions tracked by STACKLEAK"
197 default 100 195 default 100
198 range 0 4096 196 range 0 4096
199 depends on GCC_PLUGIN_STACKLEAK 197 depends on GCC_PLUGIN_STACKLEAK
200 help 198 help
201 The STACKLEAK gcc plugin instruments 199 The STACKLEAK gcc plugin instruments the kernel code for tracking
202 the lowest border of the kernel stac 200 the lowest border of the kernel stack (and for some other purposes).
203 It inserts the stackleak_track_stack 201 It inserts the stackleak_track_stack() call for the functions with
204 a stack frame size greater than or e 202 a stack frame size greater than or equal to this parameter.
205 If unsure, leave the default value 1 203 If unsure, leave the default value 100.
206 204
207 config STACKLEAK_METRICS 205 config STACKLEAK_METRICS
208 bool "Show STACKLEAK metrics in the /p 206 bool "Show STACKLEAK metrics in the /proc file system"
209 depends on GCC_PLUGIN_STACKLEAK 207 depends on GCC_PLUGIN_STACKLEAK
210 depends on PROC_FS 208 depends on PROC_FS
211 help 209 help
212 If this is set, STACKLEAK metrics fo 210 If this is set, STACKLEAK metrics for every task are available in
213 the /proc file system. In particular 211 the /proc file system. In particular, /proc/<pid>/stack_depth
214 shows the maximum kernel stack consu 212 shows the maximum kernel stack consumption for the current and
215 previous syscalls. Although this inf 213 previous syscalls. Although this information is not precise, it
216 can be useful for estimating the STA 214 can be useful for estimating the STACKLEAK performance impact for
217 your workloads. 215 your workloads.
218 216
219 config STACKLEAK_RUNTIME_DISABLE 217 config STACKLEAK_RUNTIME_DISABLE
220 bool "Allow runtime disabling of kerne 218 bool "Allow runtime disabling of kernel stack erasing"
221 depends on GCC_PLUGIN_STACKLEAK 219 depends on GCC_PLUGIN_STACKLEAK
222 help 220 help
223 This option provides 'stack_erasing' 221 This option provides 'stack_erasing' sysctl, which can be used in
224 runtime to control kernel stack eras 222 runtime to control kernel stack erasing for kernels built with
225 CONFIG_GCC_PLUGIN_STACKLEAK. 223 CONFIG_GCC_PLUGIN_STACKLEAK.
226 224
227 config INIT_ON_ALLOC_DEFAULT_ON 225 config INIT_ON_ALLOC_DEFAULT_ON
228 bool "Enable heap memory zeroing on al 226 bool "Enable heap memory zeroing on allocation by default"
229 depends on !KMSAN <<
230 help 227 help
231 This has the effect of setting "init 228 This has the effect of setting "init_on_alloc=1" on the kernel
232 command line. This can be disabled w 229 command line. This can be disabled with "init_on_alloc=0".
233 When "init_on_alloc" is enabled, all 230 When "init_on_alloc" is enabled, all page allocator and slab
234 allocator memory will be zeroed when 231 allocator memory will be zeroed when allocated, eliminating
235 many kinds of "uninitialized heap me 232 many kinds of "uninitialized heap memory" flaws, especially
236 heap content exposures. The performa 233 heap content exposures. The performance impact varies by
237 workload, but most cases see <1% imp 234 workload, but most cases see <1% impact. Some synthetic
238 workloads have measured as high as 7 235 workloads have measured as high as 7%.
239 236
240 config INIT_ON_FREE_DEFAULT_ON 237 config INIT_ON_FREE_DEFAULT_ON
241 bool "Enable heap memory zeroing on fr 238 bool "Enable heap memory zeroing on free by default"
242 depends on !KMSAN <<
243 help 239 help
244 This has the effect of setting "init 240 This has the effect of setting "init_on_free=1" on the kernel
245 command line. This can be disabled w 241 command line. This can be disabled with "init_on_free=0".
246 Similar to "init_on_alloc", when "in 242 Similar to "init_on_alloc", when "init_on_free" is enabled,
247 all page allocator and slab allocato 243 all page allocator and slab allocator memory will be zeroed
248 when freed, eliminating many kinds o 244 when freed, eliminating many kinds of "uninitialized heap memory"
249 flaws, especially heap content expos 245 flaws, especially heap content exposures. The primary difference
250 with "init_on_free" is that data lif 246 with "init_on_free" is that data lifetime in memory is reduced,
251 as anything freed is wiped immediate 247 as anything freed is wiped immediately, making live forensics or
252 cold boot memory attacks unable to r 248 cold boot memory attacks unable to recover freed memory contents.
253 The performance impact varies by wor 249 The performance impact varies by workload, but is more expensive
254 than "init_on_alloc" due to the nega 250 than "init_on_alloc" due to the negative cache effects of
255 touching "cold" memory areas. Most c 251 touching "cold" memory areas. Most cases see 3-5% impact. Some
256 synthetic workloads have measured as 252 synthetic workloads have measured as high as 8%.
257 253
258 config CC_HAS_ZERO_CALL_USED_REGS 254 config CC_HAS_ZERO_CALL_USED_REGS
259 def_bool $(cc-option,-fzero-call-used- 255 def_bool $(cc-option,-fzero-call-used-regs=used-gpr)
260 # https://github.com/ClangBuiltLinux/l 256 # https://github.com/ClangBuiltLinux/linux/issues/1766
261 # https://github.com/llvm/llvm-project 257 # https://github.com/llvm/llvm-project/issues/59242
262 depends on !CC_IS_CLANG || CLANG_VERSI 258 depends on !CC_IS_CLANG || CLANG_VERSION > 150006
263 259
264 config ZERO_CALL_USED_REGS 260 config ZERO_CALL_USED_REGS
265 bool "Enable register zeroing on funct 261 bool "Enable register zeroing on function exit"
266 depends on CC_HAS_ZERO_CALL_USED_REGS 262 depends on CC_HAS_ZERO_CALL_USED_REGS
267 help 263 help
268 At the end of functions, always zero 264 At the end of functions, always zero any caller-used register
269 contents. This helps ensure that tem 265 contents. This helps ensure that temporary values are not
270 leaked beyond the function boundary. 266 leaked beyond the function boundary. This means that register
271 contents are less likely to be avail 267 contents are less likely to be available for side channels
272 and information exposures. Additiona 268 and information exposures. Additionally, this helps reduce the
273 number of useful ROP gadgets by abou 269 number of useful ROP gadgets by about 20% (and removes compiler
274 generated "write-what-where" gadgets 270 generated "write-what-where" gadgets) in the resulting kernel
275 image. This has a less than 1% perfo 271 image. This has a less than 1% performance impact on most
276 workloads. Image size growth depends 272 workloads. Image size growth depends on architecture, and should
277 be evaluated for suitability. For ex 273 be evaluated for suitability. For example, x86_64 grows by less
278 than 1%, and arm64 grows by about 5% 274 than 1%, and arm64 grows by about 5%.
279 275
280 endmenu 276 endmenu
281 277
282 menu "Hardening of kernel data structures" <<
283 <<
284 config LIST_HARDENED <<
285 bool "Check integrity of linked list m <<
286 help <<
287 Minimal integrity checking in the li <<
288 to catch memory corruptions that are <<
289 immediate access fault. <<
290 <<
291 If unsure, say N. <<
292 <<
293 config BUG_ON_DATA_CORRUPTION <<
294 bool "Trigger a BUG when data corrupti <<
295 select LIST_HARDENED <<
296 help <<
297 Select this option if the kernel sho <<
298 data corruption in kernel memory str <<
299 for validity. <<
300 <<
301 If unsure, say N. <<
302 <<
303 endmenu <<
304 <<
305 config CC_HAS_RANDSTRUCT 278 config CC_HAS_RANDSTRUCT
306 def_bool $(cc-option,-frandomize-layou 279 def_bool $(cc-option,-frandomize-layout-seed-file=/dev/null)
307 # Randstruct was first added in Clang <<
308 # Clang 16 due to https://github.com/l <<
309 depends on !CC_IS_CLANG || CLANG_VERSI <<
310 280
311 choice 281 choice
312 prompt "Randomize layout of sensitive 282 prompt "Randomize layout of sensitive kernel structures"
313 default RANDSTRUCT_FULL if COMPILE_TES 283 default RANDSTRUCT_FULL if COMPILE_TEST && (GCC_PLUGINS || CC_HAS_RANDSTRUCT)
314 default RANDSTRUCT_NONE 284 default RANDSTRUCT_NONE
315 help 285 help
316 If you enable this, the layouts of s 286 If you enable this, the layouts of structures that are entirely
317 function pointers (and have not been 287 function pointers (and have not been manually annotated with
318 __no_randomize_layout), or structure 288 __no_randomize_layout), or structures that have been explicitly
319 marked with __randomize_layout, will 289 marked with __randomize_layout, will be randomized at compile-time.
320 This can introduce the requirement o 290 This can introduce the requirement of an additional information
321 exposure vulnerability for exploits 291 exposure vulnerability for exploits targeting these structure
322 types. 292 types.
323 293
324 Enabling this feature will introduce 294 Enabling this feature will introduce some performance impact,
325 slightly increase memory usage, and 295 slightly increase memory usage, and prevent the use of forensic
326 tools like Volatility against the sy 296 tools like Volatility against the system (unless the kernel
327 source tree isn't cleaned after kern 297 source tree isn't cleaned after kernel installation).
328 298
329 The seed used for compilation is in 299 The seed used for compilation is in scripts/basic/randomize.seed.
330 It remains after a "make clean" to a 300 It remains after a "make clean" to allow for external modules to
331 be compiled with the existing seed a 301 be compiled with the existing seed and will be removed by a
332 "make mrproper" or "make distclean". 302 "make mrproper" or "make distclean". This file should not be made
333 public, or the structure layout can 303 public, or the structure layout can be determined.
334 304
335 config RANDSTRUCT_NONE 305 config RANDSTRUCT_NONE
336 bool "Disable structure layout 306 bool "Disable structure layout randomization"
337 help 307 help
338 Build normally: no structure 308 Build normally: no structure layout randomization.
339 309
340 config RANDSTRUCT_FULL 310 config RANDSTRUCT_FULL
341 bool "Fully randomize structur 311 bool "Fully randomize structure layout"
342 depends on CC_HAS_RANDSTRUCT | 312 depends on CC_HAS_RANDSTRUCT || GCC_PLUGINS
343 select MODVERSIONS if MODULES !! 313 select MODVERSIONS if MODULES
344 help 314 help
345 Fully randomize the member l 315 Fully randomize the member layout of sensitive
346 structures as much as possib 316 structures as much as possible, which may have both a
347 memory size and performance 317 memory size and performance impact.
348 318
349 One difference between the C 319 One difference between the Clang and GCC plugin
350 implementations is the handl 320 implementations is the handling of bitfields. The GCC
351 plugin treats them as fully 321 plugin treats them as fully separate variables,
352 introducing sometimes signif 322 introducing sometimes significant padding. Clang tries
353 to keep adjacent bitfields t 323 to keep adjacent bitfields together, but with their bit
354 ordering randomized. 324 ordering randomized.
355 325
356 config RANDSTRUCT_PERFORMANCE 326 config RANDSTRUCT_PERFORMANCE
357 bool "Limit randomization of s 327 bool "Limit randomization of structure layout to cache-lines"
358 depends on GCC_PLUGINS 328 depends on GCC_PLUGINS
359 select MODVERSIONS if MODULES !! 329 select MODVERSIONS if MODULES
360 help 330 help
361 Randomization of sensitive k 331 Randomization of sensitive kernel structures will make a
362 best effort at restricting r 332 best effort at restricting randomization to cacheline-sized
363 groups of members. It will f 333 groups of members. It will further not randomize bitfields
364 in structures. This reduces 334 in structures. This reduces the performance hit of RANDSTRUCT
365 at the cost of weakened rand 335 at the cost of weakened randomization.
366 endchoice 336 endchoice
367 337
368 config RANDSTRUCT 338 config RANDSTRUCT
369 def_bool !RANDSTRUCT_NONE 339 def_bool !RANDSTRUCT_NONE
370 340
371 config GCC_PLUGIN_RANDSTRUCT 341 config GCC_PLUGIN_RANDSTRUCT
372 def_bool GCC_PLUGINS && RANDSTRUCT 342 def_bool GCC_PLUGINS && RANDSTRUCT
373 help 343 help
374 Use GCC plugin to randomize structur 344 Use GCC plugin to randomize structure layout.
375 345
376 This plugin was ported from grsecuri 346 This plugin was ported from grsecurity/PaX. More
377 information at: 347 information at:
378 * https://grsecurity.net/ 348 * https://grsecurity.net/
379 * https://pax.grsecurity.net/ 349 * https://pax.grsecurity.net/
380 350
381 endmenu 351 endmenu
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