1 // SPDX-License-Identifier: GPL-2.0
3 * Test cases for compiler-based stack variable zeroing via future
4 * compiler flags or CONFIG_GCC_PLUGIN_STRUCTLEAK*.
6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
8 #include <linux/init.h>
9 #include <linux/kernel.h>
10 #include <linux/module.h>
11 #include <linux/string.h>
13 /* Exfiltration buffer. */
14 #define MAX_VAR_SIZE 128
15 static u8 check_buf
[MAX_VAR_SIZE
];
17 /* Character array to trigger stack protector in all functions. */
20 /* Volatile mask to convince compiler to copy memory with 0xff. */
21 static volatile u8 forced_mask
= 0xff;
23 /* Location and size tracking to validate fill and test are colocated. */
24 static void *fill_start
, *target_start
;
25 static size_t fill_size
, target_size
;
27 static bool range_contains(char *haystack_start
, size_t haystack_size
,
28 char *needle_start
, size_t needle_size
)
30 if (needle_start
>= haystack_start
&&
31 needle_start
+ needle_size
<= haystack_start
+ haystack_size
)
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
40 #define DO_NOTHING_RETURN_SCALAR(ptr) *(ptr)
41 #define DO_NOTHING_RETURN_STRING(ptr) /**/
42 #define DO_NOTHING_RETURN_STRUCT(ptr) /**/
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))
51 #define FETCH_ARG_SCALAR(var) &var
52 #define FETCH_ARG_STRING(var) var
53 #define FETCH_ARG_STRUCT(var) &var
55 #define FILL_SIZE_STRING 16
57 #define INIT_CLONE_SCALAR /**/
58 #define INIT_CLONE_STRING [FILL_SIZE_STRING]
59 #define INIT_CLONE_STRUCT /**/
61 #define INIT_SCALAR_none /**/
62 #define INIT_SCALAR_zero = 0
64 #define INIT_STRING_none [FILL_SIZE_STRING] /**/
65 #define INIT_STRING_zero [FILL_SIZE_STRING] = { }
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, \
72 .three = arg->three, \
75 #define INIT_STRUCT_dynamic_partial = { .two = arg->two, }
76 #define INIT_STRUCT_dynamic_all = { .one = arg->one, \
78 .three = arg->three, \
81 #define INIT_STRUCT_runtime_partial ; \
83 #define INIT_STRUCT_runtime_all ; \
87 memset(&var.four, 0, \
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 * @xfail: is this test expected to fail?
97 #define DEFINE_TEST_DRIVER(name, var_type, which, xfail) \
98 /* Returns 0 on success, 1 on failure. */ \
99 static noinline __init int test_ ## name (void) \
101 var_type zero INIT_CLONE_ ## which; \
105 /* Notice when a new test is larger than expected. */ \
106 BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE); \
108 /* Fill clone type with zero for per-field init. */ \
109 memset(&zero, 0x00, sizeof(zero)); \
110 /* Clear entire check buffer for 0xFF overlap test. */ \
111 memset(check_buf, 0x00, sizeof(check_buf)); \
112 /* Fill stack with 0xFF. */ \
113 ignored = leaf_ ##name((unsigned long)&ignored, 1, \
114 FETCH_ARG_ ## which(zero)); \
115 /* Verify all bytes overwritten with 0xFF. */ \
116 for (sum = 0, i = 0; i < target_size; i++) \
117 sum += (check_buf[i] != 0xFF); \
119 pr_err(#name ": leaf fill was not 0xFF!?\n"); \
122 /* Clear entire check buffer for later bit tests. */ \
123 memset(check_buf, 0x00, sizeof(check_buf)); \
124 /* Extract stack-defined variable contents. */ \
125 ignored = leaf_ ##name((unsigned long)&ignored, 0, \
126 FETCH_ARG_ ## which(zero)); \
128 /* Validate that compiler lined up fill and target. */ \
129 if (!range_contains(fill_start, fill_size, \
130 target_start, target_size)) { \
131 pr_err(#name ": stack fill missed target!?\n"); \
132 pr_err(#name ": fill %zu wide\n", fill_size); \
133 pr_err(#name ": target offset by %d\n", \
134 (int)((ssize_t)(uintptr_t)fill_start - \
135 (ssize_t)(uintptr_t)target_start)); \
139 /* Look for any bytes still 0xFF in check region. */ \
140 for (sum = 0, i = 0; i < target_size; i++) \
141 sum += (check_buf[i] == 0xFF); \
144 pr_info(#name " ok\n"); \
147 pr_warn(#name " %sFAIL (uninit bytes: %d)\n", \
148 (xfail) ? "X" : "", sum); \
149 return (xfail) ? 0 : 1; \
152 #define DEFINE_TEST(name, var_type, which, init_level) \
153 /* no-op to force compiler into ignoring "uninitialized" vars */\
154 static noinline __init DO_NOTHING_TYPE_ ## which(var_type) \
155 do_nothing_ ## name(var_type *ptr) \
157 /* Will always be true, but compiler doesn't know. */ \
158 if ((unsigned long)ptr > 0x2) \
159 return DO_NOTHING_RETURN_ ## which(ptr); \
161 return DO_NOTHING_RETURN_ ## which(ptr + 1); \
163 static noinline __init int leaf_ ## name(unsigned long sp, \
167 char buf[VAR_BUFFER]; \
168 var_type var INIT_ ## which ## _ ## init_level; \
170 target_start = &var; \
171 target_size = sizeof(var); \
173 * Keep this buffer around to make sure we've got a \
174 * stack frame of SOME kind... \
176 memset(buf, (char)(sp & 0xff), sizeof(buf)); \
177 /* Fill variable with 0xFF. */ \
180 fill_size = sizeof(var); \
182 (char)((sp & 0xff) | forced_mask), \
186 /* Silence "never initialized" warnings. */ \
187 DO_NOTHING_CALL_ ## which(var, name); \
189 /* Exfiltrate "var". */ \
190 memcpy(check_buf, target_start, target_size); \
192 return (int)buf[0] | (int)buf[sizeof(buf) - 1]; \
194 DEFINE_TEST_DRIVER(name, var_type, which, 0)
196 /* Structure with no padding. */
204 /* Simple structure with padding likely to be covered by compiler. */
205 struct test_small_hole
{
208 /* 3 byte padding hole here. */
213 /* Try to trigger unhandled padding in a structure. */
214 struct test_aligned
{
219 struct test_big_hole
{
223 /* 61 byte padding hole here. */
224 struct test_aligned four
;
227 struct test_trailing_hole
{
232 /* "sizeof(unsigned long) - 1" byte padding hole here. */
235 /* Test if STRUCTLEAK is clearing structs with __user fields. */
243 #define DEFINE_SCALAR_TEST(name, init) \
244 DEFINE_TEST(name ## _ ## init, name, SCALAR, init)
246 #define DEFINE_SCALAR_TESTS(init) \
247 DEFINE_SCALAR_TEST(u8, init); \
248 DEFINE_SCALAR_TEST(u16, init); \
249 DEFINE_SCALAR_TEST(u32, init); \
250 DEFINE_SCALAR_TEST(u64, init); \
251 DEFINE_TEST(char_array_ ## init, unsigned char, STRING, init)
253 #define DEFINE_STRUCT_TEST(name, init) \
254 DEFINE_TEST(name ## _ ## init, \
255 struct test_ ## name, STRUCT, init)
257 #define DEFINE_STRUCT_TESTS(init) \
258 DEFINE_STRUCT_TEST(small_hole, init); \
259 DEFINE_STRUCT_TEST(big_hole, init); \
260 DEFINE_STRUCT_TEST(trailing_hole, init); \
261 DEFINE_STRUCT_TEST(packed, init)
263 /* These should be fully initialized all the time! */
264 DEFINE_SCALAR_TESTS(zero
);
265 DEFINE_STRUCT_TESTS(zero
);
266 /* Static initialization: padding may be left uninitialized. */
267 DEFINE_STRUCT_TESTS(static_partial
);
268 DEFINE_STRUCT_TESTS(static_all
);
269 /* Dynamic initialization: padding may be left uninitialized. */
270 DEFINE_STRUCT_TESTS(dynamic_partial
);
271 DEFINE_STRUCT_TESTS(dynamic_all
);
272 /* Runtime initialization: padding may be left uninitialized. */
273 DEFINE_STRUCT_TESTS(runtime_partial
);
274 DEFINE_STRUCT_TESTS(runtime_all
);
275 /* No initialization without compiler instrumentation. */
276 DEFINE_SCALAR_TESTS(none
);
277 DEFINE_STRUCT_TESTS(none
);
278 DEFINE_TEST(user
, struct test_user
, STRUCT
, none
);
281 * Check two uses through a variable declaration outside either path,
282 * which was noticed as a special case in porting earlier stack init
285 static int noinline
__leaf_switch_none(int path
, bool fill
)
292 target_size
= sizeof(var
);
295 fill_size
= sizeof(var
);
297 memset(fill_start
, forced_mask
| 0x55, fill_size
);
299 memcpy(check_buf
, target_start
, target_size
);
303 target_size
= sizeof(var
);
306 fill_size
= sizeof(var
);
308 memset(fill_start
, forced_mask
| 0xaa, fill_size
);
310 memcpy(check_buf
, target_start
, target_size
);
314 return var
& forced_mask
;
319 static noinline __init
int leaf_switch_1_none(unsigned long sp
, bool fill
,
322 return __leaf_switch_none(1, fill
);
325 static noinline __init
int leaf_switch_2_none(unsigned long sp
, bool fill
,
328 return __leaf_switch_none(2, fill
);
332 * These are expected to fail for most configurations because neither
333 * GCC nor Clang have a way to perform initialization of variables in
334 * non-code areas (i.e. in a switch statement before the first "case").
335 * https://bugs.llvm.org/show_bug.cgi?id=44916
337 DEFINE_TEST_DRIVER(switch_1_none
, uint64_t, SCALAR
, 1);
338 DEFINE_TEST_DRIVER(switch_2_none
, uint64_t, SCALAR
, 1);
340 static int __init
test_stackinit_init(void)
342 unsigned int failures
= 0;
344 #define test_scalars(init) do { \
345 failures += test_u8_ ## init (); \
346 failures += test_u16_ ## init (); \
347 failures += test_u32_ ## init (); \
348 failures += test_u64_ ## init (); \
349 failures += test_char_array_ ## init (); \
352 #define test_structs(init) do { \
353 failures += test_small_hole_ ## init (); \
354 failures += test_big_hole_ ## init (); \
355 failures += test_trailing_hole_ ## init (); \
356 failures += test_packed_ ## init (); \
359 /* These are explicitly initialized and should always pass. */
362 /* Padding here appears to be accidentally always initialized? */
363 test_structs(dynamic_partial
);
364 /* Padding initialization depends on compiler behaviors. */
365 test_structs(static_partial
);
366 test_structs(static_all
);
367 test_structs(dynamic_all
);
368 test_structs(runtime_partial
);
369 test_structs(runtime_all
);
371 /* STRUCTLEAK_BYREF_ALL should cover everything from here down. */
373 failures
+= test_switch_1_none();
374 failures
+= test_switch_2_none();
376 /* STRUCTLEAK_BYREF should cover from here down. */
379 /* STRUCTLEAK will only cover this. */
380 failures
+= test_user();
383 pr_info("all tests passed!\n");
385 pr_err("failures: %u\n", failures
);
387 return failures
? -EINVAL
: 0;
389 module_init(test_stackinit_init
);
391 static void __exit
test_stackinit_exit(void)
393 module_exit(test_stackinit_exit
);
395 MODULE_LICENSE("GPL");