1 // SPDX-License-Identifier: GPL-2.0
3 * This is for all the tests related to logic bugs (e.g. bad dereferences,
4 * bad alignment, bad loops, bad locking, bad scheduling, deep stacks, and
5 * lockups) along with other things that don't fit well into existing LKDTM
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>
16 #if IS_ENABLED(CONFIG_X86_32) && !IS_ENABLED(CONFIG_UML)
21 struct list_head node;
25 * Make sure our attempts to over run the kernel stack doesn't trigger
26 * a compiler warning when CONFIG_FRAME_WARN is set. Then make sure we
27 * recurse past the end of THREAD_SIZE by default.
29 #if defined(CONFIG_FRAME_WARN) && (CONFIG_FRAME_WARN > 0)
30 #define REC_STACK_SIZE (_AC(CONFIG_FRAME_WARN, UL) / 2)
32 #define REC_STACK_SIZE (THREAD_SIZE / 8)
34 #define REC_NUM_DEFAULT ((THREAD_SIZE / REC_STACK_SIZE) * 2)
36 static int recur_count = REC_NUM_DEFAULT;
38 static DEFINE_SPINLOCK(lock_me_up);
41 * Make sure compiler does not optimize this function or stack frame away:
42 * - function marked noinline
43 * - stack variables are marked volatile
44 * - stack variables are written (memset()) and read (pr_info())
45 * - function has external effects (pr_info())
47 static int noinline recursive_loop(int remaining)
49 volatile char buf[REC_STACK_SIZE];
51 memset((void *)buf, remaining & 0xFF, sizeof(buf));
52 pr_info("loop %d/%d ...\n", (int)buf[remaining % sizeof(buf)],
57 return recursive_loop(remaining - 1);
60 /* If the depth is negative, use the default, otherwise keep parameter. */
61 void __init lkdtm_bugs_init(int *recur_param)
64 *recur_param = recur_count;
66 recur_count = *recur_param;
69 void lkdtm_PANIC(void)
79 static int warn_counter;
81 void lkdtm_WARNING(void)
83 WARN_ON(++warn_counter);
86 void lkdtm_WARNING_MESSAGE(void)
88 WARN(1, "Warning message trigger count: %d\n", ++warn_counter);
91 void lkdtm_EXCEPTION(void)
93 *((volatile int *) 0) = 0;
102 void lkdtm_EXHAUST_STACK(void)
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");
110 static noinline void __lkdtm_CORRUPT_STACK(void *stack)
112 memset(stack, '\xff', 64);
115 /* This should trip the stack canary, not corrupt the return address. */
116 noinline void lkdtm_CORRUPT_STACK(void)
118 /* Use default char array length that triggers stack protection. */
119 char data[8] __aligned(sizeof(void *));
121 pr_info("Corrupting stack containing char array ...\n");
122 __lkdtm_CORRUPT_STACK((void *)&data);
125 /* Same as above but will only get a canary with -fstack-protector-strong */
126 noinline void lkdtm_CORRUPT_STACK_STRONG(void)
129 unsigned short shorts[4];
131 } data __aligned(sizeof(void *));
133 pr_info("Corrupting stack containing union ...\n");
134 __lkdtm_CORRUPT_STACK((void *)&data);
137 void lkdtm_UNALIGNED_LOAD_STORE_WRITE(void)
139 static u8 data[5] __attribute__((aligned(4))) = {1, 2, 3, 4, 5};
141 u32 val = 0x12345678;
143 p = (u32 *)(data + 1);
148 if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
149 pr_err("XFAIL: arch has CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS\n");
152 void lkdtm_SOFTLOCKUP(void)
159 void lkdtm_HARDLOCKUP(void)
166 void lkdtm_SPINLOCKUP(void)
168 /* Must be called twice to trigger. */
169 spin_lock(&lock_me_up);
170 /* Let sparse know we intended to exit holding the lock. */
171 __release(&lock_me_up);
174 void lkdtm_HUNG_TASK(void)
176 set_current_state(TASK_UNINTERRUPTIBLE);
180 volatile unsigned int huge = INT_MAX - 2;
181 volatile unsigned int ignored;
183 void lkdtm_OVERFLOW_SIGNED(void)
188 pr_info("Normal signed addition ...\n");
192 pr_info("Overflowing signed addition ...\n");
198 void lkdtm_OVERFLOW_UNSIGNED(void)
203 pr_info("Normal unsigned addition ...\n");
207 pr_info("Overflowing unsigned addition ...\n");
212 /* Intentionally using old-style flex array definition of 1 byte. */
213 struct array_bounds_flex_array {
219 struct array_bounds {
226 void lkdtm_ARRAY_BOUNDS(void)
228 struct array_bounds_flex_array *not_checked;
229 struct array_bounds *checked;
232 not_checked = kmalloc(sizeof(*not_checked) * 2, GFP_KERNEL);
233 checked = kmalloc(sizeof(*checked) * 2, GFP_KERNEL);
234 if (!not_checked || !checked) {
240 pr_info("Array access within bounds ...\n");
241 /* For both, touch all bytes in the actual member size. */
242 for (i = 0; i < sizeof(checked->data); i++)
243 checked->data[i] = 'A';
245 * For the uninstrumented flex array member, also touch 1 byte
246 * beyond to verify it is correctly uninstrumented.
248 for (i = 0; i < sizeof(not_checked->data) + 1; i++)
249 not_checked->data[i] = 'A';
251 pr_info("Array access beyond bounds ...\n");
252 for (i = 0; i < sizeof(checked->data) + 1; i++)
253 checked->data[i] = 'B';
257 pr_err("FAIL: survived array bounds overflow!\n");
260 void lkdtm_CORRUPT_LIST_ADD(void)
263 * Initially, an empty list via LIST_HEAD:
264 * test_head.next = &test_head
265 * test_head.prev = &test_head
267 LIST_HEAD(test_head);
268 struct lkdtm_list good, bad;
269 void *target[2] = { };
270 void *redirection = ⌖
272 pr_info("attempting good list addition\n");
275 * Adding to the list performs these actions:
276 * test_head.next->prev = &good.node
277 * good.node.next = test_head.next
278 * good.node.prev = test_head
279 * test_head.next = good.node
281 list_add(&good.node, &test_head);
283 pr_info("attempting corrupted list addition\n");
285 * In simulating this "write what where" primitive, the "what" is
286 * the address of &bad.node, and the "where" is the address held
289 test_head.next = redirection;
290 list_add(&bad.node, &test_head);
292 if (target[0] == NULL && target[1] == NULL)
293 pr_err("Overwrite did not happen, but no BUG?!\n");
295 pr_err("list_add() corruption not detected!\n");
298 void lkdtm_CORRUPT_LIST_DEL(void)
300 LIST_HEAD(test_head);
301 struct lkdtm_list item;
302 void *target[2] = { };
303 void *redirection = ⌖
305 list_add(&item.node, &test_head);
307 pr_info("attempting good list removal\n");
308 list_del(&item.node);
310 pr_info("attempting corrupted list removal\n");
311 list_add(&item.node, &test_head);
313 /* As with the list_add() test above, this corrupts "next". */
314 item.node.next = redirection;
315 list_del(&item.node);
317 if (target[0] == NULL && target[1] == NULL)
318 pr_err("Overwrite did not happen, but no BUG?!\n");
320 pr_err("list_del() corruption not detected!\n");
323 /* Test that VMAP_STACK is actually allocating with a leading guard page */
324 void lkdtm_STACK_GUARD_PAGE_LEADING(void)
326 const unsigned char *stack = task_stack_page(current);
327 const unsigned char *ptr = stack - 1;
328 volatile unsigned char byte;
330 pr_info("attempting bad read from page below current stack\n");
334 pr_err("FAIL: accessed page before stack! (byte: %x)\n", byte);
337 /* Test that VMAP_STACK is actually allocating with a trailing guard page */
338 void lkdtm_STACK_GUARD_PAGE_TRAILING(void)
340 const unsigned char *stack = task_stack_page(current);
341 const unsigned char *ptr = stack + THREAD_SIZE;
342 volatile unsigned char byte;
344 pr_info("attempting bad read from page above current stack\n");
348 pr_err("FAIL: accessed page after stack! (byte: %x)\n", byte);
351 void lkdtm_UNSET_SMEP(void)
353 #if IS_ENABLED(CONFIG_X86_64) && !IS_ENABLED(CONFIG_UML)
354 #define MOV_CR4_DEPTH 64
355 void (*direct_write_cr4)(unsigned long val);
360 cr4 = native_read_cr4();
362 if ((cr4 & X86_CR4_SMEP) != X86_CR4_SMEP) {
363 pr_err("FAIL: SMEP not in use\n");
366 cr4 &= ~(X86_CR4_SMEP);
368 pr_info("trying to clear SMEP normally\n");
369 native_write_cr4(cr4);
370 if (cr4 == native_read_cr4()) {
371 pr_err("FAIL: pinning SMEP failed!\n");
373 pr_info("restoring SMEP\n");
374 native_write_cr4(cr4);
377 pr_info("ok: SMEP did not get cleared\n");
380 * To test the post-write pinning verification we need to call
381 * directly into the middle of native_write_cr4() where the
382 * cr4 write happens, skipping any pinning. This searches for
383 * the cr4 writing instruction.
385 insn = (unsigned char *)native_write_cr4;
386 for (i = 0; i < MOV_CR4_DEPTH; i++) {
388 if (insn[i] == 0x0f && insn[i+1] == 0x22 && insn[i+2] == 0xe7)
390 /* mov %rdi,%rax; mov %rax, %cr4 */
391 if (insn[i] == 0x48 && insn[i+1] == 0x89 &&
392 insn[i+2] == 0xf8 && insn[i+3] == 0x0f &&
393 insn[i+4] == 0x22 && insn[i+5] == 0xe0)
396 if (i >= MOV_CR4_DEPTH) {
397 pr_info("ok: cannot locate cr4 writing call gadget\n");
400 direct_write_cr4 = (void *)(insn + i);
402 pr_info("trying to clear SMEP with call gadget\n");
403 direct_write_cr4(cr4);
404 if (native_read_cr4() & X86_CR4_SMEP) {
405 pr_info("ok: SMEP removal was reverted\n");
407 pr_err("FAIL: cleared SMEP not detected!\n");
409 pr_info("restoring SMEP\n");
410 native_write_cr4(cr4);
413 pr_err("XFAIL: this test is x86_64-only\n");
417 void lkdtm_DOUBLE_FAULT(void)
419 #if IS_ENABLED(CONFIG_X86_32) && !IS_ENABLED(CONFIG_UML)
421 * Trigger #DF by setting the stack limit to zero. This clobbers
422 * a GDT TLS slot, which is okay because the current task will die
423 * anyway due to the double fault.
425 struct desc_struct d = {
426 .type = 3, /* expand-up, writable, accessed data */
427 .p = 1, /* present */
429 .g = 0, /* limit in bytes */
430 .s = 1, /* not system */
434 write_gdt_entry(get_cpu_gdt_rw(smp_processor_id()),
435 GDT_ENTRY_TLS_MIN, &d, DESCTYPE_S);
438 * Put our zero-limit segment in SS and then trigger a fault. The
439 * 4-byte access to (%esp) will fault with #SS, and the attempt to
440 * deliver the fault will recursively cause #SS and result in #DF.
441 * This whole process happens while NMIs and MCEs are blocked by the
442 * MOV SS window. This is nice because an NMI with an invalid SS
443 * would also double-fault, resulting in the NMI or MCE being lost.
445 asm volatile ("movw %0, %%ss; addl $0, (%%esp)" ::
446 "r" ((unsigned short)(GDT_ENTRY_TLS_MIN << 3)));
448 pr_err("FAIL: tried to double fault but didn't die\n");
450 pr_err("XFAIL: this test is ia32-only\n");
455 static noinline void change_pac_parameters(void)
457 if (IS_ENABLED(CONFIG_ARM64_PTR_AUTH)) {
458 /* Reset the keys of current task */
459 ptrauth_thread_init_kernel(current);
460 ptrauth_thread_switch_kernel(current);
465 noinline void lkdtm_CORRUPT_PAC(void)
468 #define CORRUPT_PAC_ITERATE 10
471 if (!IS_ENABLED(CONFIG_ARM64_PTR_AUTH))
472 pr_err("FAIL: kernel not built with CONFIG_ARM64_PTR_AUTH\n");
474 if (!system_supports_address_auth()) {
475 pr_err("FAIL: CPU lacks pointer authentication feature\n");
479 pr_info("changing PAC parameters to force function return failure...\n");
481 * PAC is a hash value computed from input keys, return address and
482 * stack pointer. As pac has fewer bits so there is a chance of
483 * collision, so iterate few times to reduce the collision probability.
485 for (i = 0; i < CORRUPT_PAC_ITERATE; i++)
486 change_pac_parameters();
488 pr_err("FAIL: survived PAC changes! Kernel may be unstable from here\n");
490 pr_err("XFAIL: this test is arm64-only\n");