1 // SPDX-License-Identifier: GPL-2.0
2 /*
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
6 * test source files.
7 */
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
15 struct lkdtm_list {
16 struct list_head node;
17 };
18
19 /*
20 * Make sure our attempts to over run the kernel stack doesn't trigger
21 * a compiler warning when CONFIG_FRAME_WARN is set. Then make sure we
22 * recurse past the end of THREAD_SIZE by default.
23 */
24 #if defined(CONFIG_FRAME_WARN) && (CONFIG_FRAME_WARN > 0)
25 #define REC_STACK_SIZE (CONFIG_FRAME_WARN / 2)
26 #else
27 #define REC_STACK_SIZE (THREAD_SIZE / 8)
28 #endif
29 #define REC_NUM_DEFAULT ((THREAD_SIZE / REC_STACK_SIZE) * 2)
30
31 static int recur_count = REC_NUM_DEFAULT;
32
33 static DEFINE_SPINLOCK(lock_me_up);
34
recursive_loop(int remaining)35 static int recursive_loop(int remaining)
36 {
37 char buf[REC_STACK_SIZE];
38
39 /* Make sure compiler does not optimize this away. */
40 memset(buf, (remaining & 0xff) | 0x1, REC_STACK_SIZE);
41 if (!remaining)
42 return 0;
43 else
44 return recursive_loop(remaining - 1);
45 }
46
47 /* If the depth is negative, use the default, otherwise keep parameter. */
lkdtm_bugs_init(int * recur_param)48 void __init lkdtm_bugs_init(int *recur_param)
49 {
50 if (*recur_param < 0)
51 *recur_param = recur_count;
52 else
53 recur_count = *recur_param;
54 }
55
lkdtm_PANIC(void)56 void lkdtm_PANIC(void)
57 {
58 panic("dumptest");
59 }
60
lkdtm_BUG(void)61 void lkdtm_BUG(void)
62 {
63 BUG();
64 }
65
lkdtm_WARNING(void)66 void lkdtm_WARNING(void)
67 {
68 WARN_ON(1);
69 }
70
lkdtm_EXCEPTION(void)71 void lkdtm_EXCEPTION(void)
72 {
73 *((volatile int *) 0) = 0;
74 }
75
lkdtm_LOOP(void)76 void lkdtm_LOOP(void)
77 {
78 for (;;)
79 ;
80 }
81
lkdtm_OVERFLOW(void)82 void lkdtm_OVERFLOW(void)
83 {
84 (void) recursive_loop(recur_count);
85 }
86
__lkdtm_CORRUPT_STACK(void * stack)87 static noinline void __lkdtm_CORRUPT_STACK(void *stack)
88 {
89 memset(stack, '\xff', 64);
90 }
91
92 /* This should trip the stack canary, not corrupt the return address. */
lkdtm_CORRUPT_STACK(void)93 noinline void lkdtm_CORRUPT_STACK(void)
94 {
95 /* Use default char array length that triggers stack protection. */
96 char data[8] __aligned(sizeof(void *));
97
98 __lkdtm_CORRUPT_STACK(&data);
99
100 pr_info("Corrupted stack containing char array ...\n");
101 }
102
103 /* Same as above but will only get a canary with -fstack-protector-strong */
lkdtm_CORRUPT_STACK_STRONG(void)104 noinline void lkdtm_CORRUPT_STACK_STRONG(void)
105 {
106 union {
107 unsigned short shorts[4];
108 unsigned long *ptr;
109 } data __aligned(sizeof(void *));
110
111 __lkdtm_CORRUPT_STACK(&data);
112
113 pr_info("Corrupted stack containing union ...\n");
114 }
115
lkdtm_UNALIGNED_LOAD_STORE_WRITE(void)116 void lkdtm_UNALIGNED_LOAD_STORE_WRITE(void)
117 {
118 static u8 data[5] __attribute__((aligned(4))) = {1, 2, 3, 4, 5};
119 u32 *p;
120 u32 val = 0x12345678;
121
122 p = (u32 *)(data + 1);
123 if (*p == 0)
124 val = 0x87654321;
125 *p = val;
126 }
127
lkdtm_SOFTLOCKUP(void)128 void lkdtm_SOFTLOCKUP(void)
129 {
130 preempt_disable();
131 for (;;)
132 cpu_relax();
133 }
134
lkdtm_HARDLOCKUP(void)135 void lkdtm_HARDLOCKUP(void)
136 {
137 local_irq_disable();
138 for (;;)
139 cpu_relax();
140 }
141
lkdtm_SPINLOCKUP(void)142 void lkdtm_SPINLOCKUP(void)
143 {
144 /* Must be called twice to trigger. */
145 spin_lock(&lock_me_up);
146 /* Let sparse know we intended to exit holding the lock. */
147 __release(&lock_me_up);
148 }
149
lkdtm_HUNG_TASK(void)150 void lkdtm_HUNG_TASK(void)
151 {
152 set_current_state(TASK_UNINTERRUPTIBLE);
153 schedule();
154 }
155
lkdtm_CORRUPT_LIST_ADD(void)156 void lkdtm_CORRUPT_LIST_ADD(void)
157 {
158 /*
159 * Initially, an empty list via LIST_HEAD:
160 * test_head.next = &test_head
161 * test_head.prev = &test_head
162 */
163 LIST_HEAD(test_head);
164 struct lkdtm_list good, bad;
165 void *target[2] = { };
166 void *redirection = ⌖
167
168 pr_info("attempting good list addition\n");
169
170 /*
171 * Adding to the list performs these actions:
172 * test_head.next->prev = &good.node
173 * good.node.next = test_head.next
174 * good.node.prev = test_head
175 * test_head.next = good.node
176 */
177 list_add(&good.node, &test_head);
178
179 pr_info("attempting corrupted list addition\n");
180 /*
181 * In simulating this "write what where" primitive, the "what" is
182 * the address of &bad.node, and the "where" is the address held
183 * by "redirection".
184 */
185 test_head.next = redirection;
186 list_add(&bad.node, &test_head);
187
188 if (target[0] == NULL && target[1] == NULL)
189 pr_err("Overwrite did not happen, but no BUG?!\n");
190 else
191 pr_err("list_add() corruption not detected!\n");
192 }
193
lkdtm_CORRUPT_LIST_DEL(void)194 void lkdtm_CORRUPT_LIST_DEL(void)
195 {
196 LIST_HEAD(test_head);
197 struct lkdtm_list item;
198 void *target[2] = { };
199 void *redirection = ⌖
200
201 list_add(&item.node, &test_head);
202
203 pr_info("attempting good list removal\n");
204 list_del(&item.node);
205
206 pr_info("attempting corrupted list removal\n");
207 list_add(&item.node, &test_head);
208
209 /* As with the list_add() test above, this corrupts "next". */
210 item.node.next = redirection;
211 list_del(&item.node);
212
213 if (target[0] == NULL && target[1] == NULL)
214 pr_err("Overwrite did not happen, but no BUG?!\n");
215 else
216 pr_err("list_del() corruption not detected!\n");
217 }
218
219 /* Test if unbalanced set_fs(KERNEL_DS)/set_fs(USER_DS) check exists. */
lkdtm_CORRUPT_USER_DS(void)220 void lkdtm_CORRUPT_USER_DS(void)
221 {
222 pr_info("setting bad task size limit\n");
223 set_fs(KERNEL_DS);
224
225 /* Make sure we do not keep running with a KERNEL_DS! */
226 force_sig(SIGKILL, current);
227 }
228
229 /* Test that VMAP_STACK is actually allocating with a leading guard page */
lkdtm_STACK_GUARD_PAGE_LEADING(void)230 void lkdtm_STACK_GUARD_PAGE_LEADING(void)
231 {
232 const unsigned char *stack = task_stack_page(current);
233 const unsigned char *ptr = stack - 1;
234 volatile unsigned char byte;
235
236 pr_info("attempting bad read from page below current stack\n");
237
238 byte = *ptr;
239
240 pr_err("FAIL: accessed page before stack!\n");
241 }
242
243 /* Test that VMAP_STACK is actually allocating with a trailing guard page */
lkdtm_STACK_GUARD_PAGE_TRAILING(void)244 void lkdtm_STACK_GUARD_PAGE_TRAILING(void)
245 {
246 const unsigned char *stack = task_stack_page(current);
247 const unsigned char *ptr = stack + THREAD_SIZE;
248 volatile unsigned char byte;
249
250 pr_info("attempting bad read from page above current stack\n");
251
252 byte = *ptr;
253
254 pr_err("FAIL: accessed page after stack!\n");
255 }
256