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
stackinit_range_contains(char * haystack_start,size_t haystack_size,char * needle_start,size_t needle_size)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 OPTIMIZER_HIDE_VAR(ptr); \
203 /* Will always be true, but compiler doesn't know. */ \
204 if ((unsigned long)ptr > 0x2) \
205 return DO_NOTHING_RETURN_ ## which(ptr); \
206 else \
207 return DO_NOTHING_RETURN_ ## which(ptr + 1); \
208 } \
209 static noinline int leaf_ ## name(unsigned long sp, bool fill, \
210 var_type *arg) \
211 { \
212 char buf[VAR_BUFFER]; \
213 var_type var \
214 INIT_ ## which ## _ ## init_level(var_type); \
215 \
216 target_start = &var; \
217 target_size = sizeof(var); \
218 /* \
219 * Keep this buffer around to make sure we've got a \
220 * stack frame of SOME kind... \
221 */ \
222 memset(buf, (char)(sp & 0xff), sizeof(buf)); \
223 /* Fill variable with 0xFF. */ \
224 if (fill) { \
225 fill_start = &var; \
226 fill_size = sizeof(var); \
227 memset(fill_start, \
228 (char)((sp & 0xff) | forced_mask), \
229 fill_size); \
230 } \
231 \
232 /* Silence "never initialized" warnings. */ \
233 DO_NOTHING_CALL_ ## which(var, name); \
234 \
235 /* Exfiltrate "var". */ \
236 memcpy(check_buf, target_start, target_size); \
237 \
238 return (int)buf[0] | (int)buf[sizeof(buf) - 1]; \
239 } \
240 DEFINE_TEST_DRIVER(name, var_type, which, xfail)
241
242 /* Structure with no padding. */
243 struct test_packed {
244 unsigned long one;
245 unsigned long two;
246 unsigned long three;
247 unsigned long four;
248 };
249
250 /* Simple structure with padding likely to be covered by compiler. */
251 struct test_small_hole {
252 size_t one;
253 char two;
254 /* 3 byte padding hole here. */
255 int three;
256 unsigned long four;
257 };
258
259 /* Trigger unhandled padding in a structure. */
260 struct test_big_hole {
261 u8 one;
262 u8 two;
263 u8 three;
264 /* 61 byte padding hole here. */
265 u8 four __aligned(64);
266 } __aligned(64);
267
268 struct test_trailing_hole {
269 char *one;
270 char *two;
271 char *three;
272 char four;
273 /* "sizeof(unsigned long) - 1" byte padding hole here. */
274 };
275
276 /* Test if STRUCTLEAK is clearing structs with __user fields. */
277 struct test_user {
278 u8 one;
279 unsigned long two;
280 char __user *three;
281 unsigned long four;
282 };
283
284 #define ALWAYS_PASS WANT_SUCCESS
285 #define ALWAYS_FAIL XFAIL
286
287 #ifdef CONFIG_INIT_STACK_NONE
288 # define USER_PASS XFAIL
289 # define BYREF_PASS XFAIL
290 # define STRONG_PASS XFAIL
291 #elif defined(CONFIG_GCC_PLUGIN_STRUCTLEAK_USER)
292 # define USER_PASS WANT_SUCCESS
293 # define BYREF_PASS XFAIL
294 # define STRONG_PASS XFAIL
295 #elif defined(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF)
296 # define USER_PASS WANT_SUCCESS
297 # define BYREF_PASS WANT_SUCCESS
298 # define STRONG_PASS XFAIL
299 #else
300 # define USER_PASS WANT_SUCCESS
301 # define BYREF_PASS WANT_SUCCESS
302 # define STRONG_PASS WANT_SUCCESS
303 #endif
304
305 #define DEFINE_SCALAR_TEST(name, init, xfail) \
306 DEFINE_TEST(name ## _ ## init, name, SCALAR, \
307 init, xfail)
308
309 #define DEFINE_SCALAR_TESTS(init, xfail) \
310 DEFINE_SCALAR_TEST(u8, init, xfail); \
311 DEFINE_SCALAR_TEST(u16, init, xfail); \
312 DEFINE_SCALAR_TEST(u32, init, xfail); \
313 DEFINE_SCALAR_TEST(u64, init, xfail); \
314 DEFINE_TEST(char_array_ ## init, unsigned char, \
315 STRING, init, xfail)
316
317 #define DEFINE_STRUCT_TEST(name, init, xfail) \
318 DEFINE_TEST(name ## _ ## init, \
319 struct test_ ## name, STRUCT, init, \
320 xfail)
321
322 #define DEFINE_STRUCT_TESTS(init, xfail) \
323 DEFINE_STRUCT_TEST(small_hole, init, xfail); \
324 DEFINE_STRUCT_TEST(big_hole, init, xfail); \
325 DEFINE_STRUCT_TEST(trailing_hole, init, xfail); \
326 DEFINE_STRUCT_TEST(packed, init, xfail)
327
328 #define DEFINE_STRUCT_INITIALIZER_TESTS(base, xfail) \
329 DEFINE_STRUCT_TESTS(base ## _ ## partial, \
330 xfail); \
331 DEFINE_STRUCT_TESTS(base ## _ ## all, xfail)
332
333 /* These should be fully initialized all the time! */
334 DEFINE_SCALAR_TESTS(zero, ALWAYS_PASS);
335 DEFINE_STRUCT_TESTS(zero, ALWAYS_PASS);
336 /* Struct initializers: padding may be left uninitialized. */
337 DEFINE_STRUCT_INITIALIZER_TESTS(static, STRONG_PASS);
338 DEFINE_STRUCT_INITIALIZER_TESTS(dynamic, STRONG_PASS);
339 DEFINE_STRUCT_INITIALIZER_TESTS(runtime, STRONG_PASS);
340 DEFINE_STRUCT_INITIALIZER_TESTS(assigned_static, STRONG_PASS);
341 DEFINE_STRUCT_INITIALIZER_TESTS(assigned_dynamic, STRONG_PASS);
342 DEFINE_STRUCT_TESTS(assigned_copy, ALWAYS_FAIL);
343 /* No initialization without compiler instrumentation. */
344 DEFINE_SCALAR_TESTS(none, STRONG_PASS);
345 DEFINE_STRUCT_TESTS(none, BYREF_PASS);
346 /* Initialization of members with __user attribute. */
347 DEFINE_TEST(user, struct test_user, STRUCT, none, USER_PASS);
348
349 /*
350 * Check two uses through a variable declaration outside either path,
351 * which was noticed as a special case in porting earlier stack init
352 * compiler logic.
353 */
__leaf_switch_none(int path,bool fill)354 static int noinline __leaf_switch_none(int path, bool fill)
355 {
356 switch (path) {
357 /*
358 * This is intentionally unreachable. To silence the
359 * warning, build with -Wno-switch-unreachable
360 */
361 uint64_t var[10];
362
363 case 1:
364 target_start = &var;
365 target_size = sizeof(var);
366 if (fill) {
367 fill_start = &var;
368 fill_size = sizeof(var);
369
370 memset(fill_start, forced_mask | 0x55, fill_size);
371 }
372 memcpy(check_buf, target_start, target_size);
373 break;
374 case 2:
375 target_start = &var;
376 target_size = sizeof(var);
377 if (fill) {
378 fill_start = &var;
379 fill_size = sizeof(var);
380
381 memset(fill_start, forced_mask | 0xaa, fill_size);
382 }
383 memcpy(check_buf, target_start, target_size);
384 break;
385 default:
386 var[1] = 5;
387 return var[1] & forced_mask;
388 }
389 return 0;
390 }
391
leaf_switch_1_none(unsigned long sp,bool fill,uint64_t * arg)392 static noinline int leaf_switch_1_none(unsigned long sp, bool fill,
393 uint64_t *arg)
394 {
395 return __leaf_switch_none(1, fill);
396 }
397
leaf_switch_2_none(unsigned long sp,bool fill,uint64_t * arg)398 static noinline int leaf_switch_2_none(unsigned long sp, bool fill,
399 uint64_t *arg)
400 {
401 return __leaf_switch_none(2, fill);
402 }
403
404 /*
405 * These are expected to fail for most configurations because neither
406 * GCC nor Clang have a way to perform initialization of variables in
407 * non-code areas (i.e. in a switch statement before the first "case").
408 * https://bugs.llvm.org/show_bug.cgi?id=44916
409 */
410 DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR, ALWAYS_FAIL);
411 DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR, ALWAYS_FAIL);
412
413 #define KUNIT_test_scalars(init) \
414 KUNIT_CASE(test_u8_ ## init), \
415 KUNIT_CASE(test_u16_ ## init), \
416 KUNIT_CASE(test_u32_ ## init), \
417 KUNIT_CASE(test_u64_ ## init), \
418 KUNIT_CASE(test_char_array_ ## init)
419
420 #define KUNIT_test_structs(init) \
421 KUNIT_CASE(test_small_hole_ ## init), \
422 KUNIT_CASE(test_big_hole_ ## init), \
423 KUNIT_CASE(test_trailing_hole_ ## init),\
424 KUNIT_CASE(test_packed_ ## init) \
425
426 static struct kunit_case stackinit_test_cases[] = {
427 /* These are explicitly initialized and should always pass. */
428 KUNIT_test_scalars(zero),
429 KUNIT_test_structs(zero),
430 /* Padding here appears to be accidentally always initialized? */
431 KUNIT_test_structs(dynamic_partial),
432 KUNIT_test_structs(assigned_dynamic_partial),
433 /* Padding initialization depends on compiler behaviors. */
434 KUNIT_test_structs(static_partial),
435 KUNIT_test_structs(static_all),
436 KUNIT_test_structs(dynamic_all),
437 KUNIT_test_structs(runtime_partial),
438 KUNIT_test_structs(runtime_all),
439 KUNIT_test_structs(assigned_static_partial),
440 KUNIT_test_structs(assigned_static_all),
441 KUNIT_test_structs(assigned_dynamic_all),
442 /* Everything fails this since it effectively performs a memcpy(). */
443 KUNIT_test_structs(assigned_copy),
444 /* STRUCTLEAK_BYREF_ALL should cover everything from here down. */
445 KUNIT_test_scalars(none),
446 KUNIT_CASE(test_switch_1_none),
447 KUNIT_CASE(test_switch_2_none),
448 /* STRUCTLEAK_BYREF should cover from here down. */
449 KUNIT_test_structs(none),
450 /* STRUCTLEAK will only cover this. */
451 KUNIT_CASE(test_user),
452 {}
453 };
454
455 static struct kunit_suite stackinit_test_suite = {
456 .name = "stackinit",
457 .test_cases = stackinit_test_cases,
458 };
459
460 kunit_test_suites(&stackinit_test_suite);
461
462 MODULE_LICENSE("GPL");
463