1 | // SPDX-License-Identifier: GPL-2.0-or-later |
2 | /* |
3 | * Test cases for compiler-based stack variable zeroing via |
4 | * -ftrivial-auto-var-init={zero,pattern} or CONFIG_GCC_PLUGIN_STRUCTLEAK*. |
5 | * For example, see: |
6 | * "Running tests with kunit_tool" at Documentation/dev-tools/kunit/start.rst |
7 | * ./tools/testing/kunit/kunit.py run stackinit [--raw_output] \ |
8 | * --make_option LLVM=1 \ |
9 | * --kconfig_add CONFIG_INIT_STACK_ALL_ZERO=y |
10 | * |
11 | */ |
12 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
13 | |
14 | #include <kunit/test.h> |
15 | #include <linux/init.h> |
16 | #include <linux/kernel.h> |
17 | #include <linux/module.h> |
18 | #include <linux/string.h> |
19 | |
20 | /* Exfiltration buffer. */ |
21 | #define MAX_VAR_SIZE 128 |
22 | static u8 check_buf[MAX_VAR_SIZE]; |
23 | |
24 | /* Character array to trigger stack protector in all functions. */ |
25 | #define VAR_BUFFER 32 |
26 | |
27 | /* Volatile mask to convince compiler to copy memory with 0xff. */ |
28 | static volatile u8 forced_mask = 0xff; |
29 | |
30 | /* Location and size tracking to validate fill and test are colocated. */ |
31 | static void *fill_start, *target_start; |
32 | static size_t fill_size, target_size; |
33 | |
34 | static bool stackinit_range_contains(char *haystack_start, size_t haystack_size, |
35 | char *needle_start, size_t needle_size) |
36 | { |
37 | if (needle_start >= haystack_start && |
38 | needle_start + needle_size <= haystack_start + haystack_size) |
39 | return true; |
40 | return false; |
41 | } |
42 | |
43 | /* Whether the test is expected to fail. */ |
44 | #define WANT_SUCCESS 0 |
45 | #define XFAIL 1 |
46 | |
47 | #define DO_NOTHING_TYPE_SCALAR(var_type) var_type |
48 | #define DO_NOTHING_TYPE_STRING(var_type) void |
49 | #define DO_NOTHING_TYPE_STRUCT(var_type) void |
50 | |
51 | #define DO_NOTHING_RETURN_SCALAR(ptr) *(ptr) |
52 | #define DO_NOTHING_RETURN_STRING(ptr) /**/ |
53 | #define DO_NOTHING_RETURN_STRUCT(ptr) /**/ |
54 | |
55 | #define DO_NOTHING_CALL_SCALAR(var, name) \ |
56 | (var) = do_nothing_ ## name(&(var)) |
57 | #define DO_NOTHING_CALL_STRING(var, name) \ |
58 | do_nothing_ ## name(var) |
59 | #define DO_NOTHING_CALL_STRUCT(var, name) \ |
60 | do_nothing_ ## name(&(var)) |
61 | |
62 | #define FETCH_ARG_SCALAR(var) &var |
63 | #define FETCH_ARG_STRING(var) var |
64 | #define FETCH_ARG_STRUCT(var) &var |
65 | |
66 | #define FILL_SIZE_STRING 16 |
67 | |
68 | #define INIT_CLONE_SCALAR /**/ |
69 | #define INIT_CLONE_STRING [FILL_SIZE_STRING] |
70 | #define INIT_CLONE_STRUCT /**/ |
71 | |
72 | #define ZERO_CLONE_SCALAR(zero) memset(&(zero), 0x00, sizeof(zero)) |
73 | #define ZERO_CLONE_STRING(zero) memset(&(zero), 0x00, sizeof(zero)) |
74 | /* |
75 | * For the struct, intentionally poison padding to see if it gets |
76 | * copied out in direct assignments. |
77 | * */ |
78 | #define ZERO_CLONE_STRUCT(zero) \ |
79 | do { \ |
80 | memset(&(zero), 0xFF, sizeof(zero)); \ |
81 | zero.one = 0; \ |
82 | zero.two = 0; \ |
83 | zero.three = 0; \ |
84 | zero.four = 0; \ |
85 | } while (0) |
86 | |
87 | #define INIT_SCALAR_none(var_type) /**/ |
88 | #define INIT_SCALAR_zero(var_type) = 0 |
89 | |
90 | #define INIT_STRING_none(var_type) [FILL_SIZE_STRING] /**/ |
91 | #define INIT_STRING_zero(var_type) [FILL_SIZE_STRING] = { } |
92 | |
93 | #define INIT_STRUCT_none(var_type) /**/ |
94 | #define INIT_STRUCT_zero(var_type) = { } |
95 | |
96 | |
97 | #define __static_partial { .two = 0, } |
98 | #define __static_all { .one = 0, \ |
99 | .two = 0, \ |
100 | .three = 0, \ |
101 | .four = 0, \ |
102 | } |
103 | #define __dynamic_partial { .two = arg->two, } |
104 | #define __dynamic_all { .one = arg->one, \ |
105 | .two = arg->two, \ |
106 | .three = arg->three, \ |
107 | .four = arg->four, \ |
108 | } |
109 | #define __runtime_partial var.two = 0 |
110 | #define __runtime_all var.one = 0; \ |
111 | var.two = 0; \ |
112 | var.three = 0; \ |
113 | var.four = 0 |
114 | |
115 | #define INIT_STRUCT_static_partial(var_type) \ |
116 | = __static_partial |
117 | #define INIT_STRUCT_static_all(var_type) \ |
118 | = __static_all |
119 | #define INIT_STRUCT_dynamic_partial(var_type) \ |
120 | = __dynamic_partial |
121 | #define INIT_STRUCT_dynamic_all(var_type) \ |
122 | = __dynamic_all |
123 | #define INIT_STRUCT_runtime_partial(var_type) \ |
124 | ; __runtime_partial |
125 | #define INIT_STRUCT_runtime_all(var_type) \ |
126 | ; __runtime_all |
127 | |
128 | #define INIT_STRUCT_assigned_static_partial(var_type) \ |
129 | ; var = (var_type)__static_partial |
130 | #define INIT_STRUCT_assigned_static_all(var_type) \ |
131 | ; var = (var_type)__static_all |
132 | #define INIT_STRUCT_assigned_dynamic_partial(var_type) \ |
133 | ; var = (var_type)__dynamic_partial |
134 | #define INIT_STRUCT_assigned_dynamic_all(var_type) \ |
135 | ; var = (var_type)__dynamic_all |
136 | |
137 | #define INIT_STRUCT_assigned_copy(var_type) \ |
138 | ; var = *(arg) |
139 | |
140 | /* |
141 | * @name: unique string name for the test |
142 | * @var_type: type to be tested for zeroing initialization |
143 | * @which: is this a SCALAR, STRING, or STRUCT type? |
144 | * @init_level: what kind of initialization is performed |
145 | * @xfail: is this test expected to fail? |
146 | */ |
147 | #define DEFINE_TEST_DRIVER(name, var_type, which, xfail) \ |
148 | /* Returns 0 on success, 1 on failure. */ \ |
149 | static noinline void test_ ## name (struct kunit *test) \ |
150 | { \ |
151 | var_type zero INIT_CLONE_ ## which; \ |
152 | int ignored; \ |
153 | u8 sum = 0, i; \ |
154 | \ |
155 | /* Notice when a new test is larger than expected. */ \ |
156 | BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE); \ |
157 | \ |
158 | /* Fill clone type with zero for per-field init. */ \ |
159 | ZERO_CLONE_ ## which(zero); \ |
160 | /* Clear entire check buffer for 0xFF overlap test. */ \ |
161 | memset(check_buf, 0x00, sizeof(check_buf)); \ |
162 | /* Fill stack with 0xFF. */ \ |
163 | ignored = leaf_ ##name((unsigned long)&ignored, 1, \ |
164 | FETCH_ARG_ ## which(zero)); \ |
165 | /* Verify all bytes overwritten with 0xFF. */ \ |
166 | for (sum = 0, i = 0; i < target_size; i++) \ |
167 | sum += (check_buf[i] != 0xFF); \ |
168 | KUNIT_ASSERT_EQ_MSG(test, sum, 0, \ |
169 | "leaf fill was not 0xFF!?\n"); \ |
170 | /* Clear entire check buffer for later bit tests. */ \ |
171 | memset(check_buf, 0x00, sizeof(check_buf)); \ |
172 | /* Extract stack-defined variable contents. */ \ |
173 | ignored = leaf_ ##name((unsigned long)&ignored, 0, \ |
174 | FETCH_ARG_ ## which(zero)); \ |
175 | \ |
176 | /* Validate that compiler lined up fill and target. */ \ |
177 | KUNIT_ASSERT_TRUE_MSG(test, \ |
178 | stackinit_range_contains(fill_start, fill_size, \ |
179 | target_start, target_size), \ |
180 | "stack fill missed target!? " \ |
181 | "(fill %zu wide, target offset by %d)\n", \ |
182 | fill_size, \ |
183 | (int)((ssize_t)(uintptr_t)fill_start - \ |
184 | (ssize_t)(uintptr_t)target_start)); \ |
185 | \ |
186 | /* Look for any bytes still 0xFF in check region. */ \ |
187 | for (sum = 0, i = 0; i < target_size; i++) \ |
188 | sum += (check_buf[i] == 0xFF); \ |
189 | \ |
190 | if (sum != 0 && xfail) \ |
191 | kunit_skip(test, \ |
192 | "XFAIL uninit bytes: %d\n", \ |
193 | sum); \ |
194 | KUNIT_ASSERT_EQ_MSG(test, sum, 0, \ |
195 | "uninit bytes: %d\n", sum); \ |
196 | } |
197 | #define DEFINE_TEST(name, var_type, which, init_level, xfail) \ |
198 | /* no-op to force compiler into ignoring "uninitialized" vars */\ |
199 | static noinline DO_NOTHING_TYPE_ ## which(var_type) \ |
200 | do_nothing_ ## name(var_type *ptr) \ |
201 | { \ |
202 | /* Will always be true, but compiler doesn't know. */ \ |
203 | if ((unsigned long)ptr > 0x2) \ |
204 | return DO_NOTHING_RETURN_ ## which(ptr); \ |
205 | else \ |
206 | return DO_NOTHING_RETURN_ ## which(ptr + 1); \ |
207 | } \ |
208 | static noinline int leaf_ ## name(unsigned long sp, bool fill, \ |
209 | var_type *arg) \ |
210 | { \ |
211 | char buf[VAR_BUFFER]; \ |
212 | var_type var \ |
213 | INIT_ ## which ## _ ## init_level(var_type); \ |
214 | \ |
215 | target_start = &var; \ |
216 | target_size = sizeof(var); \ |
217 | /* \ |
218 | * Keep this buffer around to make sure we've got a \ |
219 | * stack frame of SOME kind... \ |
220 | */ \ |
221 | memset(buf, (char)(sp & 0xff), sizeof(buf)); \ |
222 | /* Fill variable with 0xFF. */ \ |
223 | if (fill) { \ |
224 | fill_start = &var; \ |
225 | fill_size = sizeof(var); \ |
226 | memset(fill_start, \ |
227 | (char)((sp & 0xff) | forced_mask), \ |
228 | fill_size); \ |
229 | } \ |
230 | \ |
231 | /* Silence "never initialized" warnings. */ \ |
232 | DO_NOTHING_CALL_ ## which(var, name); \ |
233 | \ |
234 | /* Exfiltrate "var". */ \ |
235 | memcpy(check_buf, target_start, target_size); \ |
236 | \ |
237 | return (int)buf[0] | (int)buf[sizeof(buf) - 1]; \ |
238 | } \ |
239 | DEFINE_TEST_DRIVER(name, var_type, which, xfail) |
240 | |
241 | /* Structure with no padding. */ |
242 | struct test_packed { |
243 | unsigned long one; |
244 | unsigned long two; |
245 | unsigned long three; |
246 | unsigned long four; |
247 | }; |
248 | |
249 | /* Simple structure with padding likely to be covered by compiler. */ |
250 | struct test_small_hole { |
251 | size_t one; |
252 | char two; |
253 | /* 3 byte padding hole here. */ |
254 | int three; |
255 | unsigned long four; |
256 | }; |
257 | |
258 | /* Trigger unhandled padding in a structure. */ |
259 | struct test_big_hole { |
260 | u8 one; |
261 | u8 two; |
262 | u8 three; |
263 | /* 61 byte padding hole here. */ |
264 | u8 four __aligned(64); |
265 | } __aligned(64); |
266 | |
267 | struct test_trailing_hole { |
268 | char *one; |
269 | char *two; |
270 | char *three; |
271 | char four; |
272 | /* "sizeof(unsigned long) - 1" byte padding hole here. */ |
273 | }; |
274 | |
275 | /* Test if STRUCTLEAK is clearing structs with __user fields. */ |
276 | struct test_user { |
277 | u8 one; |
278 | unsigned long two; |
279 | char __user *three; |
280 | unsigned long four; |
281 | }; |
282 | |
283 | #define ALWAYS_PASS WANT_SUCCESS |
284 | #define ALWAYS_FAIL XFAIL |
285 | |
286 | #ifdef CONFIG_INIT_STACK_NONE |
287 | # define USER_PASS XFAIL |
288 | # define BYREF_PASS XFAIL |
289 | # define STRONG_PASS XFAIL |
290 | #elif defined(CONFIG_GCC_PLUGIN_STRUCTLEAK_USER) |
291 | # define USER_PASS WANT_SUCCESS |
292 | # define BYREF_PASS XFAIL |
293 | # define STRONG_PASS XFAIL |
294 | #elif defined(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF) |
295 | # define USER_PASS WANT_SUCCESS |
296 | # define BYREF_PASS WANT_SUCCESS |
297 | # define STRONG_PASS XFAIL |
298 | #else |
299 | # define USER_PASS WANT_SUCCESS |
300 | # define BYREF_PASS WANT_SUCCESS |
301 | # define STRONG_PASS WANT_SUCCESS |
302 | #endif |
303 | |
304 | #define DEFINE_SCALAR_TEST(name, init, xfail) \ |
305 | DEFINE_TEST(name ## _ ## init, name, SCALAR, \ |
306 | init, xfail) |
307 | |
308 | #define DEFINE_SCALAR_TESTS(init, xfail) \ |
309 | DEFINE_SCALAR_TEST(u8, init, xfail); \ |
310 | DEFINE_SCALAR_TEST(u16, init, xfail); \ |
311 | DEFINE_SCALAR_TEST(u32, init, xfail); \ |
312 | DEFINE_SCALAR_TEST(u64, init, xfail); \ |
313 | DEFINE_TEST(char_array_ ## init, unsigned char, \ |
314 | STRING, init, xfail) |
315 | |
316 | #define DEFINE_STRUCT_TEST(name, init, xfail) \ |
317 | DEFINE_TEST(name ## _ ## init, \ |
318 | struct test_ ## name, STRUCT, init, \ |
319 | xfail) |
320 | |
321 | #define DEFINE_STRUCT_TESTS(init, xfail) \ |
322 | DEFINE_STRUCT_TEST(small_hole, init, xfail); \ |
323 | DEFINE_STRUCT_TEST(big_hole, init, xfail); \ |
324 | DEFINE_STRUCT_TEST(trailing_hole, init, xfail); \ |
325 | DEFINE_STRUCT_TEST(packed, init, xfail) |
326 | |
327 | #define DEFINE_STRUCT_INITIALIZER_TESTS(base, xfail) \ |
328 | DEFINE_STRUCT_TESTS(base ## _ ## partial, \ |
329 | xfail); \ |
330 | DEFINE_STRUCT_TESTS(base ## _ ## all, xfail) |
331 | |
332 | /* These should be fully initialized all the time! */ |
333 | DEFINE_SCALAR_TESTS(zero, ALWAYS_PASS); |
334 | DEFINE_STRUCT_TESTS(zero, ALWAYS_PASS); |
335 | /* Struct initializers: padding may be left uninitialized. */ |
336 | DEFINE_STRUCT_INITIALIZER_TESTS(static, STRONG_PASS); |
337 | DEFINE_STRUCT_INITIALIZER_TESTS(dynamic, STRONG_PASS); |
338 | DEFINE_STRUCT_INITIALIZER_TESTS(runtime, STRONG_PASS); |
339 | DEFINE_STRUCT_INITIALIZER_TESTS(assigned_static, STRONG_PASS); |
340 | DEFINE_STRUCT_INITIALIZER_TESTS(assigned_dynamic, STRONG_PASS); |
341 | DEFINE_STRUCT_TESTS(assigned_copy, ALWAYS_FAIL); |
342 | /* No initialization without compiler instrumentation. */ |
343 | DEFINE_SCALAR_TESTS(none, STRONG_PASS); |
344 | DEFINE_STRUCT_TESTS(none, BYREF_PASS); |
345 | /* Initialization of members with __user attribute. */ |
346 | DEFINE_TEST(user, struct test_user, STRUCT, none, USER_PASS); |
347 | |
348 | /* |
349 | * Check two uses through a variable declaration outside either path, |
350 | * which was noticed as a special case in porting earlier stack init |
351 | * compiler logic. |
352 | */ |
353 | static int noinline __leaf_switch_none(int path, bool fill) |
354 | { |
355 | switch (path) { |
356 | /* |
357 | * This is intentionally unreachable. To silence the |
358 | * warning, build with -Wno-switch-unreachable |
359 | */ |
360 | uint64_t var[10]; |
361 | |
362 | case 1: |
363 | target_start = &var; |
364 | target_size = sizeof(var); |
365 | if (fill) { |
366 | fill_start = &var; |
367 | fill_size = sizeof(var); |
368 | |
369 | memset(fill_start, forced_mask | 0x55, fill_size); |
370 | } |
371 | memcpy(check_buf, target_start, target_size); |
372 | break; |
373 | case 2: |
374 | target_start = &var; |
375 | target_size = sizeof(var); |
376 | if (fill) { |
377 | fill_start = &var; |
378 | fill_size = sizeof(var); |
379 | |
380 | memset(fill_start, forced_mask | 0xaa, fill_size); |
381 | } |
382 | memcpy(check_buf, target_start, target_size); |
383 | break; |
384 | default: |
385 | var[1] = 5; |
386 | return var[1] & forced_mask; |
387 | } |
388 | return 0; |
389 | } |
390 | |
391 | static noinline int leaf_switch_1_none(unsigned long sp, bool fill, |
392 | uint64_t *arg) |
393 | { |
394 | return __leaf_switch_none(path: 1, fill); |
395 | } |
396 | |
397 | static noinline int leaf_switch_2_none(unsigned long sp, bool fill, |
398 | uint64_t *arg) |
399 | { |
400 | return __leaf_switch_none(path: 2, fill); |
401 | } |
402 | |
403 | /* |
404 | * These are expected to fail for most configurations because neither |
405 | * GCC nor Clang have a way to perform initialization of variables in |
406 | * non-code areas (i.e. in a switch statement before the first "case"). |
407 | * https://bugs.llvm.org/show_bug.cgi?id=44916 |
408 | */ |
409 | DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR, ALWAYS_FAIL); |
410 | DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR, ALWAYS_FAIL); |
411 | |
412 | #define KUNIT_test_scalars(init) \ |
413 | KUNIT_CASE(test_u8_ ## init), \ |
414 | KUNIT_CASE(test_u16_ ## init), \ |
415 | KUNIT_CASE(test_u32_ ## init), \ |
416 | KUNIT_CASE(test_u64_ ## init), \ |
417 | KUNIT_CASE(test_char_array_ ## init) |
418 | |
419 | #define KUNIT_test_structs(init) \ |
420 | KUNIT_CASE(test_small_hole_ ## init), \ |
421 | KUNIT_CASE(test_big_hole_ ## init), \ |
422 | KUNIT_CASE(test_trailing_hole_ ## init),\ |
423 | KUNIT_CASE(test_packed_ ## init) \ |
424 | |
425 | static struct kunit_case stackinit_test_cases[] = { |
426 | /* These are explicitly initialized and should always pass. */ |
427 | KUNIT_test_scalars(zero), |
428 | KUNIT_test_structs(zero), |
429 | /* Padding here appears to be accidentally always initialized? */ |
430 | KUNIT_test_structs(dynamic_partial), |
431 | KUNIT_test_structs(assigned_dynamic_partial), |
432 | /* Padding initialization depends on compiler behaviors. */ |
433 | KUNIT_test_structs(static_partial), |
434 | KUNIT_test_structs(static_all), |
435 | KUNIT_test_structs(dynamic_all), |
436 | KUNIT_test_structs(runtime_partial), |
437 | KUNIT_test_structs(runtime_all), |
438 | KUNIT_test_structs(assigned_static_partial), |
439 | KUNIT_test_structs(assigned_static_all), |
440 | KUNIT_test_structs(assigned_dynamic_all), |
441 | /* Everything fails this since it effectively performs a memcpy(). */ |
442 | KUNIT_test_structs(assigned_copy), |
443 | /* STRUCTLEAK_BYREF_ALL should cover everything from here down. */ |
444 | KUNIT_test_scalars(none), |
445 | KUNIT_CASE(test_switch_1_none), |
446 | KUNIT_CASE(test_switch_2_none), |
447 | /* STRUCTLEAK_BYREF should cover from here down. */ |
448 | KUNIT_test_structs(none), |
449 | /* STRUCTLEAK will only cover this. */ |
450 | KUNIT_CASE(test_user), |
451 | {} |
452 | }; |
453 | |
454 | static struct kunit_suite stackinit_test_suite = { |
455 | .name = "stackinit" , |
456 | .test_cases = stackinit_test_cases, |
457 | }; |
458 | |
459 | kunit_test_suites(&stackinit_test_suite); |
460 | |
461 | MODULE_LICENSE("GPL" ); |
462 | |