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 void lkdtm_WARNING(void)
  67 {
  68         WARN_ON(1);
  69 }
  70
  71 void lkdtm_EXCEPTION(void)
  72 {
  73         *((volatile int *) 0) = 0;
  74 }
  75
  76 void lkdtm_LOOP(void)
  77 {
  78         for (;;)
  79                 ;
  80 }
  81
  82 void lkdtm_OVERFLOW(void)
  83 {
  84         (void) recursive_loop(recur_count);
  85 }
  86
  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. */
  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 */
 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
 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
 128 void lkdtm_SOFTLOCKUP(void)
 129 {
 130         preempt_disable();
 131         for (;;)
 132                 cpu_relax();
 133 }
 134
 135 void lkdtm_HARDLOCKUP(void)
 136 {
 137         local_irq_disable();
 138         for (;;)
 139                 cpu_relax();
 140 }
 141
 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
 150 void lkdtm_HUNG_TASK(void)
 151 {
 152         set_current_state(TASK_UNINTERRUPTIBLE);
 153         schedule();
 154 }
 155
 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 = &target;
 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
 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 = &target;
 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. */
 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 */
 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 */
 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 }