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 	/* 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  */
__leaf_switch_none(int path,bool fill)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 
leaf_switch_1_none(unsigned long sp,bool fill,uint64_t * arg)391 static noinline int leaf_switch_1_none(unsigned long sp, bool fill,
392 					      uint64_t *arg)
393 {
394 	return __leaf_switch_none(1, fill);
395 }
396 
leaf_switch_2_none(unsigned long sp,bool fill,uint64_t * arg)397 static noinline int leaf_switch_2_none(unsigned long sp, bool fill,
398 					      uint64_t *arg)
399 {
400 	return __leaf_switch_none(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