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8#include "lkdtm.h"
9#include <linux/list.h>
10#include <linux/sched.h>
11#include <linux/sched/signal.h>
12#include <linux/sched/task_stack.h>
13#include <linux/uaccess.h>
14#include <linux/slab.h>
15
16#if IS_ENABLED(CONFIG_X86_32) && !IS_ENABLED(CONFIG_UML)
17#include <asm/desc.h>
18#endif
19
20struct lkdtm_list {
21 struct list_head node;
22};
23
24
25
26
27
28
29#if defined(CONFIG_FRAME_WARN) && (CONFIG_FRAME_WARN > 0)
30#define REC_STACK_SIZE (_AC(CONFIG_FRAME_WARN, UL) / 2)
31#else
32#define REC_STACK_SIZE (THREAD_SIZE / 8)
33#endif
34#define REC_NUM_DEFAULT ((THREAD_SIZE / REC_STACK_SIZE) * 2)
35
36static int recur_count = REC_NUM_DEFAULT;
37
38static DEFINE_SPINLOCK(lock_me_up);
39
40
41
42
43
44
45
46
47static int noinline recursive_loop(int remaining)
48{
49 volatile char buf[REC_STACK_SIZE];
50
51 memset((void *)buf, remaining & 0xFF, sizeof(buf));
52 pr_info("loop %d/%d ...\n", (int)buf[remaining % sizeof(buf)],
53 recur_count);
54 if (!remaining)
55 return 0;
56 else
57 return recursive_loop(remaining - 1);
58}
59
60
61void __init lkdtm_bugs_init(int *recur_param)
62{
63 if (*recur_param < 0)
64 *recur_param = recur_count;
65 else
66 recur_count = *recur_param;
67}
68
69void lkdtm_PANIC(void)
70{
71 panic("dumptest");
72}
73
74void lkdtm_BUG(void)
75{
76 BUG();
77}
78
79static int warn_counter;
80
81void lkdtm_WARNING(void)
82{
83 WARN_ON(++warn_counter);
84}
85
86void lkdtm_WARNING_MESSAGE(void)
87{
88 WARN(1, "Warning message trigger count: %d\n", ++warn_counter);
89}
90
91void lkdtm_EXCEPTION(void)
92{
93 *((volatile int *) 0) = 0;
94}
95
96void lkdtm_LOOP(void)
97{
98 for (;;)
99 ;
100}
101
102void lkdtm_EXHAUST_STACK(void)
103{
104 pr_info("Calling function with %lu frame size to depth %d ...\n",
105 REC_STACK_SIZE, recur_count);
106 recursive_loop(recur_count);
107 pr_info("FAIL: survived without exhausting stack?!\n");
108}
109
110static noinline void __lkdtm_CORRUPT_STACK(void *stack)
111{
112 memset(stack, '\xff', 64);
113}
114
115
116noinline void lkdtm_CORRUPT_STACK(void)
117{
118
119 char data[8] __aligned(sizeof(void *));
120
121 pr_info("Corrupting stack containing char array ...\n");
122 __lkdtm_CORRUPT_STACK((void *)&data);
123}
124
125
126noinline void lkdtm_CORRUPT_STACK_STRONG(void)
127{
128 union {
129 unsigned short shorts[4];
130 unsigned long *ptr;
131 } data __aligned(sizeof(void *));
132
133 pr_info("Corrupting stack containing union ...\n");
134 __lkdtm_CORRUPT_STACK((void *)&data);
135}
136
137static pid_t stack_pid;
138static unsigned long stack_addr;
139
140void lkdtm_REPORT_STACK(void)
141{
142 volatile uintptr_t magic;
143 pid_t pid = task_pid_nr(current);
144
145 if (pid != stack_pid) {
146 pr_info("Starting stack offset tracking for pid %d\n", pid);
147 stack_pid = pid;
148 stack_addr = (uintptr_t)&magic;
149 }
150
151 pr_info("Stack offset: %d\n", (int)(stack_addr - (uintptr_t)&magic));
152}
153
154void lkdtm_UNALIGNED_LOAD_STORE_WRITE(void)
155{
156 static u8 data[5] __attribute__((aligned(4))) = {1, 2, 3, 4, 5};
157 u32 *p;
158 u32 val = 0x12345678;
159
160 p = (u32 *)(data + 1);
161 if (*p == 0)
162 val = 0x87654321;
163 *p = val;
164
165 if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
166 pr_err("XFAIL: arch has CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS\n");
167}
168
169void lkdtm_SOFTLOCKUP(void)
170{
171 preempt_disable();
172 for (;;)
173 cpu_relax();
174}
175
176void lkdtm_HARDLOCKUP(void)
177{
178 local_irq_disable();
179 for (;;)
180 cpu_relax();
181}
182
183void lkdtm_SPINLOCKUP(void)
184{
185
186 spin_lock(&lock_me_up);
187
188 __release(&lock_me_up);
189}
190
191void lkdtm_HUNG_TASK(void)
192{
193 set_current_state(TASK_UNINTERRUPTIBLE);
194 schedule();
195}
196
197volatile unsigned int huge = INT_MAX - 2;
198volatile unsigned int ignored;
199
200void lkdtm_OVERFLOW_SIGNED(void)
201{
202 int value;
203
204 value = huge;
205 pr_info("Normal signed addition ...\n");
206 value += 1;
207 ignored = value;
208
209 pr_info("Overflowing signed addition ...\n");
210 value += 4;
211 ignored = value;
212}
213
214
215void lkdtm_OVERFLOW_UNSIGNED(void)
216{
217 unsigned int value;
218
219 value = huge;
220 pr_info("Normal unsigned addition ...\n");
221 value += 1;
222 ignored = value;
223
224 pr_info("Overflowing unsigned addition ...\n");
225 value += 4;
226 ignored = value;
227}
228
229
230struct array_bounds_flex_array {
231 int one;
232 int two;
233 char data[1];
234};
235
236struct array_bounds {
237 int one;
238 int two;
239 char data[8];
240 int three;
241};
242
243void lkdtm_ARRAY_BOUNDS(void)
244{
245 struct array_bounds_flex_array *not_checked;
246 struct array_bounds *checked;
247 volatile int i;
248
249 not_checked = kmalloc(sizeof(*not_checked) * 2, GFP_KERNEL);
250 checked = kmalloc(sizeof(*checked) * 2, GFP_KERNEL);
251
252 pr_info("Array access within bounds ...\n");
253
254 for (i = 0; i < sizeof(checked->data); i++)
255 checked->data[i] = 'A';
256
257
258
259
260 for (i = 0; i < sizeof(not_checked->data) + 1; i++)
261 not_checked->data[i] = 'A';
262
263 pr_info("Array access beyond bounds ...\n");
264 for (i = 0; i < sizeof(checked->data) + 1; i++)
265 checked->data[i] = 'B';
266
267 kfree(not_checked);
268 kfree(checked);
269 pr_err("FAIL: survived array bounds overflow!\n");
270 pr_expected_config(CONFIG_UBSAN_BOUNDS);
271}
272
273void lkdtm_CORRUPT_LIST_ADD(void)
274{
275
276
277
278
279
280 LIST_HEAD(test_head);
281 struct lkdtm_list good, bad;
282 void *target[2] = { };
283 void *redirection = ⌖
284
285 pr_info("attempting good list addition\n");
286
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291
292
293
294 list_add(&good.node, &test_head);
295
296 pr_info("attempting corrupted list addition\n");
297
298
299
300
301
302 test_head.next = redirection;
303 list_add(&bad.node, &test_head);
304
305 if (target[0] == NULL && target[1] == NULL)
306 pr_err("Overwrite did not happen, but no BUG?!\n");
307 else {
308 pr_err("list_add() corruption not detected!\n");
309 pr_expected_config(CONFIG_DEBUG_LIST);
310 }
311}
312
313void lkdtm_CORRUPT_LIST_DEL(void)
314{
315 LIST_HEAD(test_head);
316 struct lkdtm_list item;
317 void *target[2] = { };
318 void *redirection = ⌖
319
320 list_add(&item.node, &test_head);
321
322 pr_info("attempting good list removal\n");
323 list_del(&item.node);
324
325 pr_info("attempting corrupted list removal\n");
326 list_add(&item.node, &test_head);
327
328
329 item.node.next = redirection;
330 list_del(&item.node);
331
332 if (target[0] == NULL && target[1] == NULL)
333 pr_err("Overwrite did not happen, but no BUG?!\n");
334 else {
335 pr_err("list_del() corruption not detected!\n");
336 pr_expected_config(CONFIG_DEBUG_LIST);
337 }
338}
339
340
341void lkdtm_STACK_GUARD_PAGE_LEADING(void)
342{
343 const unsigned char *stack = task_stack_page(current);
344 const unsigned char *ptr = stack - 1;
345 volatile unsigned char byte;
346
347 pr_info("attempting bad read from page below current stack\n");
348
349 byte = *ptr;
350
351 pr_err("FAIL: accessed page before stack! (byte: %x)\n", byte);
352}
353
354
355void lkdtm_STACK_GUARD_PAGE_TRAILING(void)
356{
357 const unsigned char *stack = task_stack_page(current);
358 const unsigned char *ptr = stack + THREAD_SIZE;
359 volatile unsigned char byte;
360
361 pr_info("attempting bad read from page above current stack\n");
362
363 byte = *ptr;
364
365 pr_err("FAIL: accessed page after stack! (byte: %x)\n", byte);
366}
367
368void lkdtm_UNSET_SMEP(void)
369{
370#if IS_ENABLED(CONFIG_X86_64) && !IS_ENABLED(CONFIG_UML)
371#define MOV_CR4_DEPTH 64
372 void (*direct_write_cr4)(unsigned long val);
373 unsigned char *insn;
374 unsigned long cr4;
375 int i;
376
377 cr4 = native_read_cr4();
378
379 if ((cr4 & X86_CR4_SMEP) != X86_CR4_SMEP) {
380 pr_err("FAIL: SMEP not in use\n");
381 return;
382 }
383 cr4 &= ~(X86_CR4_SMEP);
384
385 pr_info("trying to clear SMEP normally\n");
386 native_write_cr4(cr4);
387 if (cr4 == native_read_cr4()) {
388 pr_err("FAIL: pinning SMEP failed!\n");
389 cr4 |= X86_CR4_SMEP;
390 pr_info("restoring SMEP\n");
391 native_write_cr4(cr4);
392 return;
393 }
394 pr_info("ok: SMEP did not get cleared\n");
395
396
397
398
399
400
401
402 insn = (unsigned char *)native_write_cr4;
403 for (i = 0; i < MOV_CR4_DEPTH; i++) {
404
405 if (insn[i] == 0x0f && insn[i+1] == 0x22 && insn[i+2] == 0xe7)
406 break;
407
408 if (insn[i] == 0x48 && insn[i+1] == 0x89 &&
409 insn[i+2] == 0xf8 && insn[i+3] == 0x0f &&
410 insn[i+4] == 0x22 && insn[i+5] == 0xe0)
411 break;
412 }
413 if (i >= MOV_CR4_DEPTH) {
414 pr_info("ok: cannot locate cr4 writing call gadget\n");
415 return;
416 }
417 direct_write_cr4 = (void *)(insn + i);
418
419 pr_info("trying to clear SMEP with call gadget\n");
420 direct_write_cr4(cr4);
421 if (native_read_cr4() & X86_CR4_SMEP) {
422 pr_info("ok: SMEP removal was reverted\n");
423 } else {
424 pr_err("FAIL: cleared SMEP not detected!\n");
425 cr4 |= X86_CR4_SMEP;
426 pr_info("restoring SMEP\n");
427 native_write_cr4(cr4);
428 }
429#else
430 pr_err("XFAIL: this test is x86_64-only\n");
431#endif
432}
433
434void lkdtm_DOUBLE_FAULT(void)
435{
436#if IS_ENABLED(CONFIG_X86_32) && !IS_ENABLED(CONFIG_UML)
437
438
439
440
441
442 struct desc_struct d = {
443 .type = 3,
444 .p = 1,
445 .d = 1,
446 .g = 0,
447 .s = 1,
448 };
449
450 local_irq_disable();
451 write_gdt_entry(get_cpu_gdt_rw(smp_processor_id()),
452 GDT_ENTRY_TLS_MIN, &d, DESCTYPE_S);
453
454
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457
458
459
460
461
462 asm volatile ("movw %0, %%ss; addl $0, (%%esp)" ::
463 "r" ((unsigned short)(GDT_ENTRY_TLS_MIN << 3)));
464
465 pr_err("FAIL: tried to double fault but didn't die\n");
466#else
467 pr_err("XFAIL: this test is ia32-only\n");
468#endif
469}
470
471#ifdef CONFIG_ARM64
472static noinline void change_pac_parameters(void)
473{
474 if (IS_ENABLED(CONFIG_ARM64_PTR_AUTH_KERNEL)) {
475
476 ptrauth_thread_init_kernel(current);
477 ptrauth_thread_switch_kernel(current);
478 }
479}
480#endif
481
482noinline void lkdtm_CORRUPT_PAC(void)
483{
484#ifdef CONFIG_ARM64
485#define CORRUPT_PAC_ITERATE 10
486 int i;
487
488 if (!IS_ENABLED(CONFIG_ARM64_PTR_AUTH_KERNEL))
489 pr_err("FAIL: kernel not built with CONFIG_ARM64_PTR_AUTH_KERNEL\n");
490
491 if (!system_supports_address_auth()) {
492 pr_err("FAIL: CPU lacks pointer authentication feature\n");
493 return;
494 }
495
496 pr_info("changing PAC parameters to force function return failure...\n");
497
498
499
500
501
502 for (i = 0; i < CORRUPT_PAC_ITERATE; i++)
503 change_pac_parameters();
504
505 pr_err("FAIL: survived PAC changes! Kernel may be unstable from here\n");
506#else
507 pr_err("XFAIL: this test is arm64-only\n");
508#endif
509}
510