drivers/misc/lkdtm_bugs.c

   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
  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. */
  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
  56 void lkdtm_PANIC(void)
  57 {
  58         panic("dumptest");
  59 }
  60
  61 void lkdtm_BUG(void)
  62 {
  63         BUG();
  64 }
  65
  66 static int warn_counter;
  67
  68 void lkdtm_WARNING(void)
  69 {
  70         WARN(1, "Warning message trigger count: %d\n", warn_counter++);
  71 }
  72
  73 void lkdtm_EXCEPTION(void)
  74 {
  75         *((volatile int *) 0) = 0;
  76 }
  77
  78 void lkdtm_LOOP(void)
  79 {
  80         for (;;)
  81                 ;
  82 }
  83
  84 void lkdtm_OVERFLOW(void)
  85 {
  86         (void) recursive_loop(recur_count);
  87 }
  88
  89 static noinline void __lkdtm_CORRUPT_STACK(void *stack)
  90 {
  91         memset(stack, '\xff', 64);
  92 }
  93
  94 /* This should trip the stack canary, not corrupt the return address. */
  95 noinline void lkdtm_CORRUPT_STACK(void)
  96 {
  97         /* Use default char array length that triggers stack protection. */
  98         char data[8] __aligned(sizeof(void *));
  99
 100         __lkdtm_CORRUPT_STACK(&data);
 101
 102         pr_info("Corrupted stack containing char array ...\n");
 103 }
 104
 105 /* Same as above but will only get a canary with -fstack-protector-strong */
 106 noinline void lkdtm_CORRUPT_STACK_STRONG(void)
 107 {
 108         union {
 109                 unsigned short shorts[4];
 110                 unsigned long *ptr;
 111         } data __aligned(sizeof(void *));
 112
 113         __lkdtm_CORRUPT_STACK(&data);
 114
 115         pr_info("Corrupted stack containing union ...\n");
 116 }
 117
 118 void lkdtm_UNALIGNED_LOAD_STORE_WRITE(void)
 119 {
 120         static u8 data[5] __attribute__((aligned(4))) = {1, 2, 3, 4, 5};
 121         u32 *p;
 122         u32 val = 0x12345678;
 123
 124         p = (u32 *)(data + 1);
 125         if (*p == 0)
 126                 val = 0x87654321;
 127         *p = val;
 128 }
 129
 130 void lkdtm_SOFTLOCKUP(void)
 131 {
 132         preempt_disable();
 133         for (;;)
 134                 cpu_relax();
 135 }
 136
 137 void lkdtm_HARDLOCKUP(void)
 138 {
 139         local_irq_disable();
 140         for (;;)
 141                 cpu_relax();
 142 }
 143
 144 void lkdtm_SPINLOCKUP(void)
 145 {
 146         /* Must be called twice to trigger. */
 147         spin_lock(&lock_me_up);
 148         /* Let sparse know we intended to exit holding the lock. */
 149         __release(&lock_me_up);
 150 }
 151
 152 void lkdtm_HUNG_TASK(void)
 153 {
 154         set_current_state(TASK_UNINTERRUPTIBLE);
 155         schedule();
 156 }
 157
 158 void lkdtm_CORRUPT_LIST_ADD(void)
 159 {
 160         /*
 161          * Initially, an empty list via LIST_HEAD:
 162          *      test_head.next = &test_head
 163          *      test_head.prev = &test_head
 164          */
 165         LIST_HEAD(test_head);
 166         struct lkdtm_list good, bad;
 167         void *target[2] = { };
 168         void *redirection = &target;
 169
 170         pr_info("attempting good list addition\n");
 171
 172         /*
 173          * Adding to the list performs these actions:
 174          *      test_head.next->prev = &good.node
 175          *      good.node.next = test_head.next
 176          *      good.node.prev = test_head
 177          *      test_head.next = good.node
 178          */
 179         list_add(&good.node, &test_head);
 180
 181         pr_info("attempting corrupted list addition\n");
 182         /*
 183          * In simulating this "write what where" primitive, the "what" is
 184          * the address of &bad.node, and the "where" is the address held
 185          * by "redirection".
 186          */
 187         test_head.next = redirection;
 188         list_add(&bad.node, &test_head);
 189
 190         if (target[0] == NULL && target[1] == NULL)
 191                 pr_err("Overwrite did not happen, but no BUG?!\n");
 192         else
 193                 pr_err("list_add() corruption not detected!\n");
 194 }
 195
 196 void lkdtm_CORRUPT_LIST_DEL(void)
 197 {
 198         LIST_HEAD(test_head);
 199         struct lkdtm_list item;
 200         void *target[2] = { };
 201         void *redirection = &target;
 202
 203         list_add(&item.node, &test_head);
 204
 205         pr_info("attempting good list removal\n");
 206         list_del(&item.node);
 207
 208         pr_info("attempting corrupted list removal\n");
 209         list_add(&item.node, &test_head);
 210
 211         /* As with the list_add() test above, this corrupts "next". */
 212         item.node.next = redirection;
 213         list_del(&item.node);
 214
 215         if (target[0] == NULL && target[1] == NULL)
 216                 pr_err("Overwrite did not happen, but no BUG?!\n");
 217         else
 218                 pr_err("list_del() corruption not detected!\n");
 219 }
 220
 221 /* Test if unbalanced set_fs(KERNEL_DS)/set_fs(USER_DS) check exists. */
 222 void lkdtm_CORRUPT_USER_DS(void)
 223 {
 224         pr_info("setting bad task size limit\n");
 225         set_fs(KERNEL_DS);
 226
 227         /* Make sure we do not keep running with a KERNEL_DS! */
 228         force_sig(SIGKILL, current);
 229 }
 230
 231 /* Test that VMAP_STACK is actually allocating with a leading guard page */
 232 void lkdtm_STACK_GUARD_PAGE_LEADING(void)
 233 {
 234         const unsigned char *stack = task_stack_page(current);
 235         const unsigned char *ptr = stack - 1;
 236         volatile unsigned char byte;
 237
 238         pr_info("attempting bad read from page below current stack\n");
 239
 240         byte = *ptr;
 241
 242         pr_err("FAIL: accessed page before stack!\n");
 243 }
 244
 245 /* Test that VMAP_STACK is actually allocating with a trailing guard page */
 246 void lkdtm_STACK_GUARD_PAGE_TRAILING(void)
 247 {
 248         const unsigned char *stack = task_stack_page(current);
 249         const unsigned char *ptr = stack + THREAD_SIZE;
 250         volatile unsigned char byte;
 251
 252         pr_info("attempting bad read from page above current stack\n");
 253
 254         byte = *ptr;
 255
 256         pr_err("FAIL: accessed page after stack!\n");
 257 }