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