1// SPDX-Licenses: GPLv2
2/*
3 * Test cases for compiler-based stack variable zeroing via future
4 * compiler flags or CONFIG_GCC_PLUGIN_STRUCTLEAK*.
5 */
6#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
7
8#include <linux/init.h>
9#include <linux/kernel.h>
10#include <linux/module.h>
11#include <linux/string.h>
12
13/* Exfiltration buffer. */
14#define MAX_VAR_SIZE 128
15static char check_buf[MAX_VAR_SIZE];
16
17/* Character array to trigger stack protector in all functions. */
18#define VAR_BUFFER 32
19
20/* Volatile mask to convince compiler to copy memory with 0xff. */
21static volatile u8 forced_mask = 0xff;
22
23/* Location and size tracking to validate fill and test are colocated. */
24static void *fill_start, *target_start;
25static size_t fill_size, target_size;
26
27static bool range_contains(char *haystack_start, size_t haystack_size,
28 char *needle_start, size_t needle_size)
29{
30 if (needle_start >= haystack_start &&
31 needle_start + needle_size <= haystack_start + haystack_size)
32 return true;
33 return false;
34}
35
36#define DO_NOTHING_TYPE_SCALAR(var_type) var_type
37#define DO_NOTHING_TYPE_STRING(var_type) void
38#define DO_NOTHING_TYPE_STRUCT(var_type) void
39
40#define DO_NOTHING_RETURN_SCALAR(ptr) *(ptr)
41#define DO_NOTHING_RETURN_STRING(ptr) /**/
42#define DO_NOTHING_RETURN_STRUCT(ptr) /**/
43
44#define DO_NOTHING_CALL_SCALAR(var, name) \
45 (var) = do_nothing_ ## name(&(var))
46#define DO_NOTHING_CALL_STRING(var, name) \
47 do_nothing_ ## name(var)
48#define DO_NOTHING_CALL_STRUCT(var, name) \
49 do_nothing_ ## name(&(var))
50
51#define FETCH_ARG_SCALAR(var) &var
52#define FETCH_ARG_STRING(var) var
53#define FETCH_ARG_STRUCT(var) &var
54
55#define FILL_SIZE_STRING 16
56
57#define INIT_CLONE_SCALAR /**/
58#define INIT_CLONE_STRING [FILL_SIZE_STRING]
59#define INIT_CLONE_STRUCT /**/
60
61#define INIT_SCALAR_none /**/
62#define INIT_SCALAR_zero = 0
63
64#define INIT_STRING_none [FILL_SIZE_STRING] /**/
65#define INIT_STRING_zero [FILL_SIZE_STRING] = { }
66
67#define INIT_STRUCT_none /**/
68#define INIT_STRUCT_zero = { }
69#define INIT_STRUCT_static_partial = { .two = 0, }
70#define INIT_STRUCT_static_all = { .one = arg->one, \
71 .two = arg->two, \
72 .three = arg->three, \
73 .four = arg->four, \
74 }
75#define INIT_STRUCT_dynamic_partial = { .two = arg->two, }
76#define INIT_STRUCT_dynamic_all = { .one = arg->one, \
77 .two = arg->two, \
78 .three = arg->three, \
79 .four = arg->four, \
80 }
81#define INIT_STRUCT_runtime_partial ; \
82 var.two = 0
83#define INIT_STRUCT_runtime_all ; \
84 var.one = 0; \
85 var.two = 0; \
86 var.three = 0; \
87 memset(&var.four, 0, \
88 sizeof(var.four))
89
90/*
91 * @name: unique string name for the test
92 * @var_type: type to be tested for zeroing initialization
93 * @which: is this a SCALAR, STRING, or STRUCT type?
94 * @init_level: what kind of initialization is performed
95 */
96#define DEFINE_TEST_DRIVER(name, var_type, which) \
97/* Returns 0 on success, 1 on failure. */ \
98static noinline __init int test_ ## name (void) \
99{ \
100 var_type zero INIT_CLONE_ ## which; \
101 int ignored; \
102 u8 sum = 0, i; \
103 \
104 /* Notice when a new test is larger than expected. */ \
105 BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE); \
106 \
107 /* Fill clone type with zero for per-field init. */ \
108 memset(&zero, 0x00, sizeof(zero)); \
109 /* Fill stack with 0xFF. */ \
110 ignored = leaf_ ##name((unsigned long)&ignored, 1, \
111 FETCH_ARG_ ## which(zero)); \
112 /* Clear entire check buffer for later bit tests. */ \
113 memset(check_buf, 0x00, sizeof(check_buf)); \
114 /* Extract stack-defined variable contents. */ \
115 ignored = leaf_ ##name((unsigned long)&ignored, 0, \
116 FETCH_ARG_ ## which(zero)); \
117 \
118 /* Validate that compiler lined up fill and target. */ \
119 if (!range_contains(fill_start, fill_size, \
120 target_start, target_size)) { \
121 pr_err(#name ": stack fill missed target!?\n"); \
122 pr_err(#name ": fill %zu wide\n", fill_size); \
123 pr_err(#name ": target offset by %d\n", \
124 (int)((ssize_t)(uintptr_t)fill_start - \
125 (ssize_t)(uintptr_t)target_start)); \
126 return 1; \
127 } \
128 \
129 /* Look for any set bits in the check region. */ \
130 for (i = 0; i < sizeof(check_buf); i++) \
131 sum += (check_buf[i] != 0); \
132 \
133 if (sum == 0) \
134 pr_info(#name " ok\n"); \
135 else \
136 pr_warn(#name " FAIL (uninit bytes: %d)\n", \
137 sum); \
138 \
139 return (sum != 0); \
140}
141#define DEFINE_TEST(name, var_type, which, init_level) \
142/* no-op to force compiler into ignoring "uninitialized" vars */\
143static noinline __init DO_NOTHING_TYPE_ ## which(var_type) \
144do_nothing_ ## name(var_type *ptr) \
145{ \
146 /* Will always be true, but compiler doesn't know. */ \
147 if ((unsigned long)ptr > 0x2) \
148 return DO_NOTHING_RETURN_ ## which(ptr); \
149 else \
150 return DO_NOTHING_RETURN_ ## which(ptr + 1); \
151} \
152static noinline __init int leaf_ ## name(unsigned long sp, \
153 bool fill, \
154 var_type *arg) \
155{ \
156 char buf[VAR_BUFFER]; \
157 var_type var INIT_ ## which ## _ ## init_level; \
158 \
159 target_start = &var; \
160 target_size = sizeof(var); \
161 /* \
162 * Keep this buffer around to make sure we've got a \
163 * stack frame of SOME kind... \
164 */ \
165 memset(buf, (char)(sp && 0xff), sizeof(buf)); \
166 /* Fill variable with 0xFF. */ \
167 if (fill) { \
168 fill_start = &var; \
169 fill_size = sizeof(var); \
170 memset(fill_start, \
171 (char)((sp && 0xff) | forced_mask), \
172 fill_size); \
173 } \
174 \
175 /* Silence "never initialized" warnings. */ \
176 DO_NOTHING_CALL_ ## which(var, name); \
177 \
178 /* Exfiltrate "var". */ \
179 memcpy(check_buf, target_start, target_size); \
180 \
181 return (int)buf[0] | (int)buf[sizeof(buf) - 1]; \
182} \
183DEFINE_TEST_DRIVER(name, var_type, which)
184
185/* Structure with no padding. */
186struct test_packed {
187 unsigned long one;
188 unsigned long two;
189 unsigned long three;
190 unsigned long four;
191};
192
193/* Simple structure with padding likely to be covered by compiler. */
194struct test_small_hole {
195 size_t one;
196 char two;
197 /* 3 byte padding hole here. */
198 int three;
199 unsigned long four;
200};
201
202/* Try to trigger unhandled padding in a structure. */
203struct test_aligned {
204 u32 internal1;
205 u64 internal2;
206} __aligned(64);
207
208struct test_big_hole {
209 u8 one;
210 u8 two;
211 u8 three;
212 /* 61 byte padding hole here. */
213 struct test_aligned four;
214} __aligned(64);
215
216struct test_trailing_hole {
217 char *one;
218 char *two;
219 char *three;
220 char four;
221 /* "sizeof(unsigned long) - 1" byte padding hole here. */
222};
223
224/* Test if STRUCTLEAK is clearing structs with __user fields. */
225struct test_user {
226 u8 one;
227 unsigned long two;
228 char __user *three;
229 unsigned long four;
230};
231
232#define DEFINE_SCALAR_TEST(name, init) \
233 DEFINE_TEST(name ## _ ## init, name, SCALAR, init)
234
235#define DEFINE_SCALAR_TESTS(init) \
236 DEFINE_SCALAR_TEST(u8, init); \
237 DEFINE_SCALAR_TEST(u16, init); \
238 DEFINE_SCALAR_TEST(u32, init); \
239 DEFINE_SCALAR_TEST(u64, init); \
240 DEFINE_TEST(char_array_ ## init, unsigned char, STRING, init)
241
242#define DEFINE_STRUCT_TEST(name, init) \
243 DEFINE_TEST(name ## _ ## init, \
244 struct test_ ## name, STRUCT, init)
245
246#define DEFINE_STRUCT_TESTS(init) \
247 DEFINE_STRUCT_TEST(small_hole, init); \
248 DEFINE_STRUCT_TEST(big_hole, init); \
249 DEFINE_STRUCT_TEST(trailing_hole, init); \
250 DEFINE_STRUCT_TEST(packed, init)
251
252/* These should be fully initialized all the time! */
253DEFINE_SCALAR_TESTS(zero);
254DEFINE_STRUCT_TESTS(zero);
255/* Static initialization: padding may be left uninitialized. */
256DEFINE_STRUCT_TESTS(static_partial);
257DEFINE_STRUCT_TESTS(static_all);
258/* Dynamic initialization: padding may be left uninitialized. */
259DEFINE_STRUCT_TESTS(dynamic_partial);
260DEFINE_STRUCT_TESTS(dynamic_all);
261/* Runtime initialization: padding may be left uninitialized. */
262DEFINE_STRUCT_TESTS(runtime_partial);
263DEFINE_STRUCT_TESTS(runtime_all);
264/* No initialization without compiler instrumentation. */
265DEFINE_SCALAR_TESTS(none);
266DEFINE_STRUCT_TESTS(none);
267DEFINE_TEST(user, struct test_user, STRUCT, none);
268
269/*
270 * Check two uses through a variable declaration outside either path,
271 * which was noticed as a special case in porting earlier stack init
272 * compiler logic.
273 */
274static int noinline __leaf_switch_none(int path, bool fill)
275{
276 switch (path) {
277 uint64_t var;
278
279 case 1:
280 target_start = &var;
281 target_size = sizeof(var);
282 if (fill) {
283 fill_start = &var;
284 fill_size = sizeof(var);
285
286 memset(fill_start, forced_mask | 0x55, fill_size);
287 }
288 memcpy(check_buf, target_start, target_size);
289 break;
290 case 2:
291 target_start = &var;
292 target_size = sizeof(var);
293 if (fill) {
294 fill_start = &var;
295 fill_size = sizeof(var);
296
297 memset(fill_start, forced_mask | 0xaa, fill_size);
298 }
299 memcpy(check_buf, target_start, target_size);
300 break;
301 default:
302 var = 5;
303 return var & forced_mask;
304 }
305 return 0;
306}
307
308static noinline __init int leaf_switch_1_none(unsigned long sp, bool fill,
309 uint64_t *arg)
310{
311 return __leaf_switch_none(1, fill);
312}
313
314static noinline __init int leaf_switch_2_none(unsigned long sp, bool fill,
315 uint64_t *arg)
316{
317 return __leaf_switch_none(2, fill);
318}
319
320DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR);
321DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR);
322
323static int __init test_stackinit_init(void)
324{
325 unsigned int failures = 0;
326
327#define test_scalars(init) do { \
328 failures += test_u8_ ## init (); \
329 failures += test_u16_ ## init (); \
330 failures += test_u32_ ## init (); \
331 failures += test_u64_ ## init (); \
332 failures += test_char_array_ ## init (); \
333 } while (0)
334
335#define test_structs(init) do { \
336 failures += test_small_hole_ ## init (); \
337 failures += test_big_hole_ ## init (); \
338 failures += test_trailing_hole_ ## init (); \
339 failures += test_packed_ ## init (); \
340 } while (0)
341
342 /* These are explicitly initialized and should always pass. */
343 test_scalars(zero);
344 test_structs(zero);
345 /* Padding here appears to be accidentally always initialized? */
346 test_structs(dynamic_partial);
347 /* Padding initialization depends on compiler behaviors. */
348 test_structs(static_partial);
349 test_structs(static_all);
350 test_structs(dynamic_all);
351 test_structs(runtime_partial);
352 test_structs(runtime_all);
353
354 /* STRUCTLEAK_BYREF_ALL should cover everything from here down. */
355 test_scalars(none);
356 failures += test_switch_1_none();
357 failures += test_switch_2_none();
358
359 /* STRUCTLEAK_BYREF should cover from here down. */
360 test_structs(none);
361
362 /* STRUCTLEAK will only cover this. */
363 failures += test_user();
364
365 if (failures == 0)
366 pr_info("all tests passed!\n");
367 else
368 pr_err("failures: %u\n", failures);
369
370 return failures ? -EINVAL : 0;
371}
372module_init(test_stackinit_init);
373
374static void __exit test_stackinit_exit(void)
375{ }
376module_exit(test_stackinit_exit);
377
378MODULE_LICENSE("GPL");
379