1// SPDX-License-Identifier: GPL-2.0
  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 u8 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	/* Clear entire check buffer for 0xFF overlap test. */	\
110	memset(check_buf, 0x00, sizeof(check_buf));		\
111	/* Fill stack with 0xFF. */				\
112	ignored = leaf_ ##name((unsigned long)&ignored, 1,	\
113				FETCH_ARG_ ## which(zero));	\
114	/* Verify all bytes overwritten with 0xFF. */		\
115	for (sum = 0, i = 0; i < target_size; i++)		\
116		sum += (check_buf[i] != 0xFF);			\
117	if (sum) {						\
118		pr_err(#name ": leaf fill was not 0xFF!?\n");	\
119		return 1;					\
120	}							\
121	/* Clear entire check buffer for later bit tests. */	\
122	memset(check_buf, 0x00, sizeof(check_buf));		\
123	/* Extract stack-defined variable contents. */		\
124	ignored = leaf_ ##name((unsigned long)&ignored, 0,	\
125				FETCH_ARG_ ## which(zero));	\
126								\
127	/* Validate that compiler lined up fill and target. */	\
128	if (!range_contains(fill_start, fill_size,		\
129			    target_start, target_size)) {	\
130		pr_err(#name ": stack fill missed target!?\n");	\
131		pr_err(#name ": fill %zu wide\n", fill_size);	\
132		pr_err(#name ": target offset by %d\n",	\
133			(int)((ssize_t)(uintptr_t)fill_start -	\
134			(ssize_t)(uintptr_t)target_start));	\
135		return 1;					\
136	}							\
137								\
138	/* Look for any bytes still 0xFF in check region. */	\
139	for (sum = 0, i = 0; i < target_size; i++)		\
140		sum += (check_buf[i] == 0xFF);			\
141								\
142	if (sum == 0)						\
143		pr_info(#name " ok\n");				\
144	else							\
145		pr_warn(#name " FAIL (uninit bytes: %d)\n",	\
146			sum);					\
147								\
148	return (sum != 0);					\
149}
150#define DEFINE_TEST(name, var_type, which, init_level)		\
151/* no-op to force compiler into ignoring "uninitialized" vars */\
152static noinline __init DO_NOTHING_TYPE_ ## which(var_type)	\
153do_nothing_ ## name(var_type *ptr)				\
154{								\
155	/* Will always be true, but compiler doesn't know. */	\
156	if ((unsigned long)ptr > 0x2)				\
157		return DO_NOTHING_RETURN_ ## which(ptr);	\
158	else							\
159		return DO_NOTHING_RETURN_ ## which(ptr + 1);	\
160}								\
161static noinline __init int leaf_ ## name(unsigned long sp,	\
162					 bool fill,		\
163					 var_type *arg)		\
164{								\
165	char buf[VAR_BUFFER];					\
166	var_type var INIT_ ## which ## _ ## init_level;		\
167								\
168	target_start = &var;					\
169	target_size = sizeof(var);				\
170	/*							\
171	 * Keep this buffer around to make sure we've got a	\
172	 * stack frame of SOME kind...				\
173	 */							\
174	memset(buf, (char)(sp & 0xff), sizeof(buf));		\
175	/* Fill variable with 0xFF. */				\
176	if (fill) {						\
177		fill_start = &var;				\
178		fill_size = sizeof(var);			\
179		memset(fill_start,				\
180		       (char)((sp & 0xff) | forced_mask),	\
181		       fill_size);				\
182	}							\
183								\
184	/* Silence "never initialized" warnings. */		\
185	DO_NOTHING_CALL_ ## which(var, name);			\
186								\
187	/* Exfiltrate "var". */					\
188	memcpy(check_buf, target_start, target_size);		\
189								\
190	return (int)buf[0] | (int)buf[sizeof(buf) - 1];		\
191}								\
192DEFINE_TEST_DRIVER(name, var_type, which)
193
194/* Structure with no padding. */
195struct test_packed {
196	unsigned long one;
197	unsigned long two;
198	unsigned long three;
199	unsigned long four;
200};
201
202/* Simple structure with padding likely to be covered by compiler. */
203struct test_small_hole {
204	size_t one;
205	char two;
206	/* 3 byte padding hole here. */
207	int three;
208	unsigned long four;
209};
210
211/* Try to trigger unhandled padding in a structure. */
212struct test_aligned {
213	u32 internal1;
214	u64 internal2;
215} __aligned(64);
216
217struct test_big_hole {
218	u8 one;
219	u8 two;
220	u8 three;
221	/* 61 byte padding hole here. */
222	struct test_aligned four;
223} __aligned(64);
224
225struct test_trailing_hole {
226	char *one;
227	char *two;
228	char *three;
229	char four;
230	/* "sizeof(unsigned long) - 1" byte padding hole here. */
231};
232
233/* Test if STRUCTLEAK is clearing structs with __user fields. */
234struct test_user {
235	u8 one;
236	unsigned long two;
237	char __user *three;
238	unsigned long four;
239};
240
241#define DEFINE_SCALAR_TEST(name, init)				\
242		DEFINE_TEST(name ## _ ## init, name, SCALAR, init)
243
244#define DEFINE_SCALAR_TESTS(init)				\
245		DEFINE_SCALAR_TEST(u8, init);			\
246		DEFINE_SCALAR_TEST(u16, init);			\
247		DEFINE_SCALAR_TEST(u32, init);			\
248		DEFINE_SCALAR_TEST(u64, init);			\
249		DEFINE_TEST(char_array_ ## init, unsigned char, STRING, init)
250
251#define DEFINE_STRUCT_TEST(name, init)				\
252		DEFINE_TEST(name ## _ ## init,			\
253			    struct test_ ## name, STRUCT, init)
254
255#define DEFINE_STRUCT_TESTS(init)				\
256		DEFINE_STRUCT_TEST(small_hole, init);		\
257		DEFINE_STRUCT_TEST(big_hole, init);		\
258		DEFINE_STRUCT_TEST(trailing_hole, init);	\
259		DEFINE_STRUCT_TEST(packed, init)
260
261/* These should be fully initialized all the time! */
262DEFINE_SCALAR_TESTS(zero);
263DEFINE_STRUCT_TESTS(zero);
264/* Static initialization: padding may be left uninitialized. */
265DEFINE_STRUCT_TESTS(static_partial);
266DEFINE_STRUCT_TESTS(static_all);
267/* Dynamic initialization: padding may be left uninitialized. */
268DEFINE_STRUCT_TESTS(dynamic_partial);
269DEFINE_STRUCT_TESTS(dynamic_all);
270/* Runtime initialization: padding may be left uninitialized. */
271DEFINE_STRUCT_TESTS(runtime_partial);
272DEFINE_STRUCT_TESTS(runtime_all);
273/* No initialization without compiler instrumentation. */
274DEFINE_SCALAR_TESTS(none);
275DEFINE_STRUCT_TESTS(none);
276DEFINE_TEST(user, struct test_user, STRUCT, none);
277
278/*
279 * Check two uses through a variable declaration outside either path,
280 * which was noticed as a special case in porting earlier stack init
281 * compiler logic.
282 */
283static int noinline __leaf_switch_none(int path, bool fill)
284{
285	switch (path) {
286		uint64_t var;
287
288	case 1:
289		target_start = &var;
290		target_size = sizeof(var);
291		if (fill) {
292			fill_start = &var;
293			fill_size = sizeof(var);
294
295			memset(fill_start, forced_mask | 0x55, fill_size);
296		}
297		memcpy(check_buf, target_start, target_size);
298		break;
299	case 2:
300		target_start = &var;
301		target_size = sizeof(var);
302		if (fill) {
303			fill_start = &var;
304			fill_size = sizeof(var);
305
306			memset(fill_start, forced_mask | 0xaa, fill_size);
307		}
308		memcpy(check_buf, target_start, target_size);
309		break;
310	default:
311		var = 5;
312		return var & forced_mask;
313	}
314	return 0;
315}
316
317static noinline __init int leaf_switch_1_none(unsigned long sp, bool fill,
318					      uint64_t *arg)
319{
320	return __leaf_switch_none(1, fill);
321}
322
323static noinline __init int leaf_switch_2_none(unsigned long sp, bool fill,
324					      uint64_t *arg)
325{
326	return __leaf_switch_none(2, fill);
327}
328
329DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR);
330DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR);
331
332static int __init test_stackinit_init(void)
333{
334	unsigned int failures = 0;
335
336#define test_scalars(init)	do {				\
337		failures += test_u8_ ## init ();		\
338		failures += test_u16_ ## init ();		\
339		failures += test_u32_ ## init ();		\
340		failures += test_u64_ ## init ();		\
341		failures += test_char_array_ ## init ();	\
342	} while (0)
343
344#define test_structs(init)	do {				\
345		failures += test_small_hole_ ## init ();	\
346		failures += test_big_hole_ ## init ();		\
347		failures += test_trailing_hole_ ## init ();	\
348		failures += test_packed_ ## init ();		\
349	} while (0)
350
351	/* These are explicitly initialized and should always pass. */
352	test_scalars(zero);
353	test_structs(zero);
354	/* Padding here appears to be accidentally always initialized? */
355	test_structs(dynamic_partial);
356	/* Padding initialization depends on compiler behaviors. */
357	test_structs(static_partial);
358	test_structs(static_all);
359	test_structs(dynamic_all);
360	test_structs(runtime_partial);
361	test_structs(runtime_all);
362
363	/* STRUCTLEAK_BYREF_ALL should cover everything from here down. */
364	test_scalars(none);
365	failures += test_switch_1_none();
366	failures += test_switch_2_none();
367
368	/* STRUCTLEAK_BYREF should cover from here down. */
369	test_structs(none);
370
371	/* STRUCTLEAK will only cover this. */
372	failures += test_user();
373
374	if (failures == 0)
375		pr_info("all tests passed!\n");
376	else
377		pr_err("failures: %u\n", failures);
378
379	return failures ? -EINVAL : 0;
380}
381module_init(test_stackinit_init);
382
383static void __exit test_stackinit_exit(void)
384{ }
385module_exit(test_stackinit_exit);
386
387MODULE_LICENSE("GPL");