Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
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 *
6 * External build example:
7 * clang -O2 -Wall -ftrivial-auto-var-init=pattern \
8 * -o test_stackinit test_stackinit.c
9 */
10#ifdef __KERNEL__
11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12
13#include <linux/init.h>
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/string.h>
17
18#else
19
20/* Userspace headers. */
21#include <stdio.h>
22#include <stdint.h>
23#include <string.h>
24#include <stdbool.h>
25#include <errno.h>
26#include <sys/types.h>
27
28/* Linux kernel-ism stubs for stand-alone userspace build. */
29#define KBUILD_MODNAME "stackinit"
30#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
31#define pr_err(fmt, ...) fprintf(stderr, pr_fmt(fmt), ##__VA_ARGS__)
32#define pr_warn(fmt, ...) fprintf(stderr, pr_fmt(fmt), ##__VA_ARGS__)
33#define pr_info(fmt, ...) fprintf(stdout, pr_fmt(fmt), ##__VA_ARGS__)
34#define __init /**/
35#define __exit /**/
36#define __user /**/
37#define noinline __attribute__((__noinline__))
38#define __aligned(x) __attribute__((__aligned__(x)))
39#ifdef __clang__
40# define __compiletime_error(message) /**/
41#else
42# define __compiletime_error(message) __attribute__((__error__(message)))
43#endif
44#define __compiletime_assert(condition, msg, prefix, suffix) \
45 do { \
46 extern void prefix ## suffix(void) __compiletime_error(msg); \
47 if (!(condition)) \
48 prefix ## suffix(); \
49 } while (0)
50#define _compiletime_assert(condition, msg, prefix, suffix) \
51 __compiletime_assert(condition, msg, prefix, suffix)
52#define compiletime_assert(condition, msg) \
53 _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
54#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
55#define BUILD_BUG_ON(condition) \
56 BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
57typedef uint8_t u8;
58typedef uint16_t u16;
59typedef uint32_t u32;
60typedef uint64_t u64;
61
62#define module_init(func) static int (*do_init)(void) = func
63#define module_exit(func) static void (*do_exit)(void) = func
64#define MODULE_LICENSE(str) int main(void) { \
65 int rc; \
66 /* License: str */ \
67 rc = do_init(); \
68 if (rc == 0) \
69 do_exit(); \
70 return rc; \
71 }
72
73#endif /* __KERNEL__ */
74
75/* Exfiltration buffer. */
76#define MAX_VAR_SIZE 128
77static u8 check_buf[MAX_VAR_SIZE];
78
79/* Character array to trigger stack protector in all functions. */
80#define VAR_BUFFER 32
81
82/* Volatile mask to convince compiler to copy memory with 0xff. */
83static volatile u8 forced_mask = 0xff;
84
85/* Location and size tracking to validate fill and test are colocated. */
86static void *fill_start, *target_start;
87static size_t fill_size, target_size;
88
89static bool range_contains(char *haystack_start, size_t haystack_size,
90 char *needle_start, size_t needle_size)
91{
92 if (needle_start >= haystack_start &&
93 needle_start + needle_size <= haystack_start + haystack_size)
94 return true;
95 return false;
96}
97
98/* Whether the test is expected to fail. */
99#define WANT_SUCCESS 0
100#define XFAIL 1
101
102#define DO_NOTHING_TYPE_SCALAR(var_type) var_type
103#define DO_NOTHING_TYPE_STRING(var_type) void
104#define DO_NOTHING_TYPE_STRUCT(var_type) void
105
106#define DO_NOTHING_RETURN_SCALAR(ptr) *(ptr)
107#define DO_NOTHING_RETURN_STRING(ptr) /**/
108#define DO_NOTHING_RETURN_STRUCT(ptr) /**/
109
110#define DO_NOTHING_CALL_SCALAR(var, name) \
111 (var) = do_nothing_ ## name(&(var))
112#define DO_NOTHING_CALL_STRING(var, name) \
113 do_nothing_ ## name(var)
114#define DO_NOTHING_CALL_STRUCT(var, name) \
115 do_nothing_ ## name(&(var))
116
117#define FETCH_ARG_SCALAR(var) &var
118#define FETCH_ARG_STRING(var) var
119#define FETCH_ARG_STRUCT(var) &var
120
121#define FILL_SIZE_STRING 16
122
123#define INIT_CLONE_SCALAR /**/
124#define INIT_CLONE_STRING [FILL_SIZE_STRING]
125#define INIT_CLONE_STRUCT /**/
126
127#define ZERO_CLONE_SCALAR(zero) memset(&(zero), 0x00, sizeof(zero))
128#define ZERO_CLONE_STRING(zero) memset(&(zero), 0x00, sizeof(zero))
129/*
130 * For the struct, intentionally poison padding to see if it gets
131 * copied out in direct assignments.
132 * */
133#define ZERO_CLONE_STRUCT(zero) \
134 do { \
135 memset(&(zero), 0xFF, sizeof(zero)); \
136 zero.one = 0; \
137 zero.two = 0; \
138 zero.three = 0; \
139 zero.four = 0; \
140 } while (0)
141
142#define INIT_SCALAR_none(var_type) /**/
143#define INIT_SCALAR_zero(var_type) = 0
144
145#define INIT_STRING_none(var_type) [FILL_SIZE_STRING] /**/
146#define INIT_STRING_zero(var_type) [FILL_SIZE_STRING] = { }
147
148#define INIT_STRUCT_none(var_type) /**/
149#define INIT_STRUCT_zero(var_type) = { }
150
151
152#define __static_partial { .two = 0, }
153#define __static_all { .one = 0, \
154 .two = 0, \
155 .three = 0, \
156 .four = 0, \
157 }
158#define __dynamic_partial { .two = arg->two, }
159#define __dynamic_all { .one = arg->one, \
160 .two = arg->two, \
161 .three = arg->three, \
162 .four = arg->four, \
163 }
164#define __runtime_partial var.two = 0
165#define __runtime_all var.one = 0; \
166 var.two = 0; \
167 var.three = 0; \
168 var.four = 0
169
170#define INIT_STRUCT_static_partial(var_type) \
171 = __static_partial
172#define INIT_STRUCT_static_all(var_type) \
173 = __static_all
174#define INIT_STRUCT_dynamic_partial(var_type) \
175 = __dynamic_partial
176#define INIT_STRUCT_dynamic_all(var_type) \
177 = __dynamic_all
178#define INIT_STRUCT_runtime_partial(var_type) \
179 ; __runtime_partial
180#define INIT_STRUCT_runtime_all(var_type) \
181 ; __runtime_all
182
183#define INIT_STRUCT_assigned_static_partial(var_type) \
184 ; var = (var_type)__static_partial
185#define INIT_STRUCT_assigned_static_all(var_type) \
186 ; var = (var_type)__static_all
187#define INIT_STRUCT_assigned_dynamic_partial(var_type) \
188 ; var = (var_type)__dynamic_partial
189#define INIT_STRUCT_assigned_dynamic_all(var_type) \
190 ; var = (var_type)__dynamic_all
191
192#define INIT_STRUCT_assigned_copy(var_type) \
193 ; var = *(arg)
194
195/*
196 * @name: unique string name for the test
197 * @var_type: type to be tested for zeroing initialization
198 * @which: is this a SCALAR, STRING, or STRUCT type?
199 * @init_level: what kind of initialization is performed
200 * @xfail: is this test expected to fail?
201 */
202#define DEFINE_TEST_DRIVER(name, var_type, which, xfail) \
203/* Returns 0 on success, 1 on failure. */ \
204static noinline __init int test_ ## name (void) \
205{ \
206 var_type zero INIT_CLONE_ ## which; \
207 int ignored; \
208 u8 sum = 0, i; \
209 \
210 /* Notice when a new test is larger than expected. */ \
211 BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE); \
212 \
213 /* Fill clone type with zero for per-field init. */ \
214 ZERO_CLONE_ ## which(zero); \
215 /* Clear entire check buffer for 0xFF overlap test. */ \
216 memset(check_buf, 0x00, sizeof(check_buf)); \
217 /* Fill stack with 0xFF. */ \
218 ignored = leaf_ ##name((unsigned long)&ignored, 1, \
219 FETCH_ARG_ ## which(zero)); \
220 /* Verify all bytes overwritten with 0xFF. */ \
221 for (sum = 0, i = 0; i < target_size; i++) \
222 sum += (check_buf[i] != 0xFF); \
223 if (sum) { \
224 pr_err(#name ": leaf fill was not 0xFF!?\n"); \
225 return 1; \
226 } \
227 /* Clear entire check buffer for later bit tests. */ \
228 memset(check_buf, 0x00, sizeof(check_buf)); \
229 /* Extract stack-defined variable contents. */ \
230 ignored = leaf_ ##name((unsigned long)&ignored, 0, \
231 FETCH_ARG_ ## which(zero)); \
232 \
233 /* Validate that compiler lined up fill and target. */ \
234 if (!range_contains(fill_start, fill_size, \
235 target_start, target_size)) { \
236 pr_err(#name ": stack fill missed target!?\n"); \
237 pr_err(#name ": fill %zu wide\n", fill_size); \
238 pr_err(#name ": target offset by %d\n", \
239 (int)((ssize_t)(uintptr_t)fill_start - \
240 (ssize_t)(uintptr_t)target_start)); \
241 return 1; \
242 } \
243 \
244 /* Look for any bytes still 0xFF in check region. */ \
245 for (sum = 0, i = 0; i < target_size; i++) \
246 sum += (check_buf[i] == 0xFF); \
247 \
248 if (sum == 0) { \
249 pr_info(#name " ok\n"); \
250 return 0; \
251 } else { \
252 pr_warn(#name " %sFAIL (uninit bytes: %d)\n", \
253 (xfail) ? "X" : "", sum); \
254 return (xfail) ? 0 : 1; \
255 } \
256}
257#define DEFINE_TEST(name, var_type, which, init_level, xfail) \
258/* no-op to force compiler into ignoring "uninitialized" vars */\
259static noinline __init DO_NOTHING_TYPE_ ## which(var_type) \
260do_nothing_ ## name(var_type *ptr) \
261{ \
262 /* Will always be true, but compiler doesn't know. */ \
263 if ((unsigned long)ptr > 0x2) \
264 return DO_NOTHING_RETURN_ ## which(ptr); \
265 else \
266 return DO_NOTHING_RETURN_ ## which(ptr + 1); \
267} \
268static noinline __init int leaf_ ## name(unsigned long sp, \
269 bool fill, \
270 var_type *arg) \
271{ \
272 char buf[VAR_BUFFER]; \
273 var_type var \
274 INIT_ ## which ## _ ## init_level(var_type); \
275 \
276 target_start = &var; \
277 target_size = sizeof(var); \
278 /* \
279 * Keep this buffer around to make sure we've got a \
280 * stack frame of SOME kind... \
281 */ \
282 memset(buf, (char)(sp & 0xff), sizeof(buf)); \
283 /* Fill variable with 0xFF. */ \
284 if (fill) { \
285 fill_start = &var; \
286 fill_size = sizeof(var); \
287 memset(fill_start, \
288 (char)((sp & 0xff) | forced_mask), \
289 fill_size); \
290 } \
291 \
292 /* Silence "never initialized" warnings. */ \
293 DO_NOTHING_CALL_ ## which(var, name); \
294 \
295 /* Exfiltrate "var". */ \
296 memcpy(check_buf, target_start, target_size); \
297 \
298 return (int)buf[0] | (int)buf[sizeof(buf) - 1]; \
299} \
300DEFINE_TEST_DRIVER(name, var_type, which, xfail)
301
302/* Structure with no padding. */
303struct test_packed {
304 unsigned long one;
305 unsigned long two;
306 unsigned long three;
307 unsigned long four;
308};
309
310/* Simple structure with padding likely to be covered by compiler. */
311struct test_small_hole {
312 size_t one;
313 char two;
314 /* 3 byte padding hole here. */
315 int three;
316 unsigned long four;
317};
318
319/* Trigger unhandled padding in a structure. */
320struct test_big_hole {
321 u8 one;
322 u8 two;
323 u8 three;
324 /* 61 byte padding hole here. */
325 u8 four __aligned(64);
326} __aligned(64);
327
328struct test_trailing_hole {
329 char *one;
330 char *two;
331 char *three;
332 char four;
333 /* "sizeof(unsigned long) - 1" byte padding hole here. */
334};
335
336/* Test if STRUCTLEAK is clearing structs with __user fields. */
337struct test_user {
338 u8 one;
339 unsigned long two;
340 char __user *three;
341 unsigned long four;
342};
343
344#define DEFINE_SCALAR_TEST(name, init, xfail) \
345 DEFINE_TEST(name ## _ ## init, name, SCALAR, \
346 init, xfail)
347
348#define DEFINE_SCALAR_TESTS(init, xfail) \
349 DEFINE_SCALAR_TEST(u8, init, xfail); \
350 DEFINE_SCALAR_TEST(u16, init, xfail); \
351 DEFINE_SCALAR_TEST(u32, init, xfail); \
352 DEFINE_SCALAR_TEST(u64, init, xfail); \
353 DEFINE_TEST(char_array_ ## init, unsigned char, \
354 STRING, init, xfail)
355
356#define DEFINE_STRUCT_TEST(name, init, xfail) \
357 DEFINE_TEST(name ## _ ## init, \
358 struct test_ ## name, STRUCT, init, \
359 xfail)
360
361#define DEFINE_STRUCT_TESTS(init, xfail) \
362 DEFINE_STRUCT_TEST(small_hole, init, xfail); \
363 DEFINE_STRUCT_TEST(big_hole, init, xfail); \
364 DEFINE_STRUCT_TEST(trailing_hole, init, xfail); \
365 DEFINE_STRUCT_TEST(packed, init, xfail)
366
367#define DEFINE_STRUCT_INITIALIZER_TESTS(base) \
368 DEFINE_STRUCT_TESTS(base ## _ ## partial, \
369 WANT_SUCCESS); \
370 DEFINE_STRUCT_TESTS(base ## _ ## all, \
371 WANT_SUCCESS)
372
373/* These should be fully initialized all the time! */
374DEFINE_SCALAR_TESTS(zero, WANT_SUCCESS);
375DEFINE_STRUCT_TESTS(zero, WANT_SUCCESS);
376/* Struct initializers: padding may be left uninitialized. */
377DEFINE_STRUCT_INITIALIZER_TESTS(static);
378DEFINE_STRUCT_INITIALIZER_TESTS(dynamic);
379DEFINE_STRUCT_INITIALIZER_TESTS(runtime);
380DEFINE_STRUCT_INITIALIZER_TESTS(assigned_static);
381DEFINE_STRUCT_INITIALIZER_TESTS(assigned_dynamic);
382DEFINE_STRUCT_TESTS(assigned_copy, XFAIL);
383/* No initialization without compiler instrumentation. */
384DEFINE_SCALAR_TESTS(none, WANT_SUCCESS);
385DEFINE_STRUCT_TESTS(none, WANT_SUCCESS);
386/* Initialization of members with __user attribute. */
387DEFINE_TEST(user, struct test_user, STRUCT, none, WANT_SUCCESS);
388
389/*
390 * Check two uses through a variable declaration outside either path,
391 * which was noticed as a special case in porting earlier stack init
392 * compiler logic.
393 */
394static int noinline __leaf_switch_none(int path, bool fill)
395{
396 switch (path) {
397 /*
398 * This is intentionally unreachable. To silence the
399 * warning, build with -Wno-switch-unreachable
400 */
401 uint64_t var;
402
403 case 1:
404 target_start = &var;
405 target_size = sizeof(var);
406 if (fill) {
407 fill_start = &var;
408 fill_size = sizeof(var);
409
410 memset(fill_start, forced_mask | 0x55, fill_size);
411 }
412 memcpy(check_buf, target_start, target_size);
413 break;
414 case 2:
415 target_start = &var;
416 target_size = sizeof(var);
417 if (fill) {
418 fill_start = &var;
419 fill_size = sizeof(var);
420
421 memset(fill_start, forced_mask | 0xaa, fill_size);
422 }
423 memcpy(check_buf, target_start, target_size);
424 break;
425 default:
426 var = 5;
427 return var & forced_mask;
428 }
429 return 0;
430}
431
432static noinline __init int leaf_switch_1_none(unsigned long sp, bool fill,
433 uint64_t *arg)
434{
435 return __leaf_switch_none(1, fill);
436}
437
438static noinline __init int leaf_switch_2_none(unsigned long sp, bool fill,
439 uint64_t *arg)
440{
441 return __leaf_switch_none(2, fill);
442}
443
444/*
445 * These are expected to fail for most configurations because neither
446 * GCC nor Clang have a way to perform initialization of variables in
447 * non-code areas (i.e. in a switch statement before the first "case").
448 * https://bugs.llvm.org/show_bug.cgi?id=44916
449 */
450DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR, XFAIL);
451DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR, XFAIL);
452
453static int __init test_stackinit_init(void)
454{
455 unsigned int failures = 0;
456
457#define test_scalars(init) do { \
458 failures += test_u8_ ## init (); \
459 failures += test_u16_ ## init (); \
460 failures += test_u32_ ## init (); \
461 failures += test_u64_ ## init (); \
462 failures += test_char_array_ ## init (); \
463 } while (0)
464
465#define test_structs(init) do { \
466 failures += test_small_hole_ ## init (); \
467 failures += test_big_hole_ ## init (); \
468 failures += test_trailing_hole_ ## init (); \
469 failures += test_packed_ ## init (); \
470 } while (0)
471
472 /* These are explicitly initialized and should always pass. */
473 test_scalars(zero);
474 test_structs(zero);
475 /* Padding here appears to be accidentally always initialized? */
476 test_structs(dynamic_partial);
477 test_structs(assigned_dynamic_partial);
478 /* Padding initialization depends on compiler behaviors. */
479 test_structs(static_partial);
480 test_structs(static_all);
481 test_structs(dynamic_all);
482 test_structs(runtime_partial);
483 test_structs(runtime_all);
484 test_structs(assigned_static_partial);
485 test_structs(assigned_static_all);
486 test_structs(assigned_dynamic_all);
487 /* Everything fails this since it effectively performs a memcpy(). */
488 test_structs(assigned_copy);
489
490 /* STRUCTLEAK_BYREF_ALL should cover everything from here down. */
491 test_scalars(none);
492 failures += test_switch_1_none();
493 failures += test_switch_2_none();
494
495 /* STRUCTLEAK_BYREF should cover from here down. */
496 test_structs(none);
497
498 /* STRUCTLEAK will only cover this. */
499 failures += test_user();
500
501 if (failures == 0)
502 pr_info("all tests passed!\n");
503 else
504 pr_err("failures: %u\n", failures);
505
506 return failures ? -EINVAL : 0;
507}
508module_init(test_stackinit_init);
509
510static void __exit test_stackinit_exit(void)
511{ }
512module_exit(test_stackinit_exit);
513
514MODULE_LICENSE("GPL");