Quelle  heap.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0
/*
 * This is for all the tests relating directly to heap memory, including
 * page allocation and slab allocations.
 */
#include "lkdtm.h"
#include <linux/kfence.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/sched.h>

static struct kmem_cache *double_free_cache;
static struct kmem_cache *a_cache;
static struct kmem_cache *b_cache;

/*
 * Using volatile here means the compiler cannot ever make assumptions
 * about this value. This means compile-time length checks involving
 * this variable cannot be performed; only run-time checks.
 */
static volatile int __offset = 1;

/*
 * If there aren't guard pages, it's likely that a consecutive allocation will
 * let us overflow into the second allocation without overwriting something real.
 *
 * This should always be caught because there is an unconditional unmapped
 * page after vmap allocations.
 */
static void lkdtm_VMALLOC_LINEAR_OVERFLOW(void)
{
 char *one, *two;

 one = vzalloc(PAGE_SIZE);
 OPTIMIZER_HIDE_VAR(one);
 two = vzalloc(PAGE_SIZE);

 pr_info("Attempting vmalloc linear overflow ...\n");
 memset(one, 0xAA, PAGE_SIZE + __offset);

 vfree(two);
 vfree(one);
}

/*
 * This tries to stay within the next largest power-of-2 kmalloc cache
 * to avoid actually overwriting anything important if it's not detected
 * correctly.
 *
 * This should get caught by either memory tagging, KASan, or by using
 * CONFIG_SLUB_DEBUG=y and slab_debug=ZF (or CONFIG_SLUB_DEBUG_ON=y).
 */
static void lkdtm_SLAB_LINEAR_OVERFLOW(void)
{
 size_t len = 1020;
 u32 *data = kmalloc(len, GFP_KERNEL);
 if (!data)
  return;

 pr_info("Attempting slab linear overflow ...\n");
 OPTIMIZER_HIDE_VAR(data);
 data[1024 / sizeof(u32)] = 0x12345678;
 kfree(data);
}

static void lkdtm_WRITE_AFTER_FREE(void)
{
 int *base, *again;
 size_t len = 1024;
 /*
 * The slub allocator uses the first word to store the free
 * pointer in some configurations. Use the middle of the
 * allocation to avoid running into the freelist
 */
 size_t offset = (len / sizeof(*base)) / 2;

 base = kmalloc(len, GFP_KERNEL);
 if (!base)
  return;
 pr_info("Allocated memory %p-%p\n", base, &base[offset * 2]);
 pr_info("Attempting bad write to freed memory at %p\n",
  &base[offset]);
 kfree(base);
 base[offset] = 0x0abcdef0;
 /* Attempt to notice the overwrite. */
 again = kmalloc(len, GFP_KERNEL);
 kfree(again);
 if (again != base)
  pr_info("Hmm, didn't get the same memory range.\n");
}

static void lkdtm_READ_AFTER_FREE(void)
{
 int *base, *val, saw;
 size_t len = 1024;
 /*
 * The slub allocator will use the either the first word or
 * the middle of the allocation to store the free pointer,
 * depending on configurations. Store in the second word to
 * avoid running into the freelist.
 */
 size_t offset = sizeof(*base);

 base = kmalloc(len, GFP_KERNEL);
 if (!base) {
  pr_info("Unable to allocate base memory.\n");
  return;
 }

 val = kmalloc(len, GFP_KERNEL);
 if (!val) {
  pr_info("Unable to allocate val memory.\n");
  kfree(base);
  return;
 }

 *val = 0x12345678;
 base[offset] = *val;
 pr_info("Value in memory before free: %x\n", base[offset]);

 kfree(base);

 pr_info("Attempting bad read from freed memory\n");
 saw = base[offset];
 if (saw != *val) {
  /* Good! Poisoning happened, so declare a win. */
  pr_info("Memory correctly poisoned (%x)\n", saw);
 } else {
  pr_err("FAIL: Memory was not poisoned!\n");
  pr_expected_config_param(CONFIG_INIT_ON_FREE_DEFAULT_ON, "init_on_free");
 }

 kfree(val);
}

static void lkdtm_KFENCE_READ_AFTER_FREE(void)
{
 int *base, val, saw;
 unsigned long timeout, resched_after;
 size_t len = 1024;
 /*
 * The slub allocator will use the either the first word or
 * the middle of the allocation to store the free pointer,
 * depending on configurations. Store in the second word to
 * avoid running into the freelist.
 */
 size_t offset = sizeof(*base);

 /*
 * 100x the sample interval should be more than enough to ensure we get
 * a KFENCE allocation eventually.
 */
 timeout = jiffies + msecs_to_jiffies(100 * kfence_sample_interval);
 /*
 * Especially for non-preemption kernels, ensure the allocation-gate
 * timer can catch up: after @resched_after, every failed allocation
 * attempt yields, to ensure the allocation-gate timer is scheduled.
 */
 resched_after = jiffies + msecs_to_jiffies(kfence_sample_interval);
 do {
  base = kmalloc(len, GFP_KERNEL);
  if (!base) {
   pr_err("FAIL: Unable to allocate kfence memory!\n");
   return;
  }

  if (is_kfence_address(base)) {
   val = 0x12345678;
   base[offset] = val;
   pr_info("Value in memory before free: %x\n", base[offset]);

   kfree(base);

   pr_info("Attempting bad read from freed memory\n");
   saw = base[offset];
   if (saw != val) {
    /* Good! Poisoning happened, so declare a win. */
    pr_info("Memory correctly poisoned (%x)\n", saw);
   } else {
    pr_err("FAIL: Memory was not poisoned!\n");
    pr_expected_config_param(CONFIG_INIT_ON_FREE_DEFAULT_ON, "init_on_free");
   }
   return;
  }

  kfree(base);
  if (time_after(jiffies, resched_after))
   cond_resched();
 } while (time_before(jiffies, timeout));

 pr_err("FAIL: kfence memory never allocated!\n");
}

static void lkdtm_WRITE_BUDDY_AFTER_FREE(void)
{
 unsigned long p = __get_free_page(GFP_KERNEL);
 if (!p) {
  pr_info("Unable to allocate free page\n");
  return;
 }

 pr_info("Writing to the buddy page before free\n");
 memset((void *)p, 0x3, PAGE_SIZE);
 free_page(p);
 schedule();
 pr_info("Attempting bad write to the buddy page after free\n");
 memset((void *)p, 0x78, PAGE_SIZE);
 /* Attempt to notice the overwrite. */
 p = __get_free_page(GFP_KERNEL);
 free_page(p);
 schedule();
}

static void lkdtm_READ_BUDDY_AFTER_FREE(void)
{
 unsigned long p = __get_free_page(GFP_KERNEL);
 int saw, *val;
 int *base;

 if (!p) {
  pr_info("Unable to allocate free page\n");
  return;
 }

 val = kmalloc(1024, GFP_KERNEL);
 if (!val) {
  pr_info("Unable to allocate val memory.\n");
  free_page(p);
  return;
 }

 base = (int *)p;

 *val = 0x12345678;
 base[0] = *val;
 pr_info("Value in memory before free: %x\n", base[0]);
 free_page(p);
 pr_info("Attempting to read from freed memory\n");
 saw = base[0];
 if (saw != *val) {
  /* Good! Poisoning happened, so declare a win. */
  pr_info("Memory correctly poisoned (%x)\n", saw);
 } else {
  pr_err("FAIL: Buddy page was not poisoned!\n");
  pr_expected_config_param(CONFIG_INIT_ON_FREE_DEFAULT_ON, "init_on_free");
 }

 kfree(val);
}

static void lkdtm_SLAB_INIT_ON_ALLOC(void)
{
 u8 *first;
 u8 *val;

 first = kmalloc(512, GFP_KERNEL);
 if (!first) {
  pr_info("Unable to allocate 512 bytes the first time.\n");
  return;
 }

 memset(first, 0xAB, 512);
 kfree(first);

 val = kmalloc(512, GFP_KERNEL);
 if (!val) {
  pr_info("Unable to allocate 512 bytes the second time.\n");
  return;
 }
 if (val != first) {
  pr_warn("Reallocation missed clobbered memory.\n");
 }

 if (memchr(val, 0xAB, 512) == NULL) {
  pr_info("Memory appears initialized (%x, no earlier values)\n", *val);
 } else {
  pr_err("FAIL: Slab was not initialized\n");
  pr_expected_config_param(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, "init_on_alloc");
 }
 kfree(val);
}

static void lkdtm_BUDDY_INIT_ON_ALLOC(void)
{
 u8 *first;
 u8 *val;

 first = (u8 *)__get_free_page(GFP_KERNEL);
 if (!first) {
  pr_info("Unable to allocate first free page\n");
  return;
 }

 memset(first, 0xAB, PAGE_SIZE);
 free_page((unsigned long)first);

 val = (u8 *)__get_free_page(GFP_KERNEL);
 if (!val) {
  pr_info("Unable to allocate second free page\n");
  return;
 }

 if (val != first) {
  pr_warn("Reallocation missed clobbered memory.\n");
 }

 if (memchr(val, 0xAB, PAGE_SIZE) == NULL) {
  pr_info("Memory appears initialized (%x, no earlier values)\n", *val);
 } else {
  pr_err("FAIL: Slab was not initialized\n");
  pr_expected_config_param(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, "init_on_alloc");
 }
 free_page((unsigned long)val);
}

static void lkdtm_SLAB_FREE_DOUBLE(void)
{
 int *val;

 val = kmem_cache_alloc(double_free_cache, GFP_KERNEL);
 if (!val) {
  pr_info("Unable to allocate double_free_cache memory.\n");
  return;
 }

 /* Just make sure we got real memory. */
 *val = 0x12345678;
 pr_info("Attempting double slab free ...\n");
 kmem_cache_free(double_free_cache, val);
 kmem_cache_free(double_free_cache, val);
}

static void lkdtm_SLAB_FREE_CROSS(void)
{
 int *val;

 val = kmem_cache_alloc(a_cache, GFP_KERNEL);
 if (!val) {
  pr_info("Unable to allocate a_cache memory.\n");
  return;
 }

 /* Just make sure we got real memory. */
 *val = 0x12345679;
 pr_info("Attempting cross-cache slab free ...\n");
 kmem_cache_free(b_cache, val);
}

static void lkdtm_SLAB_FREE_PAGE(void)
{
 unsigned long p = __get_free_page(GFP_KERNEL);

 pr_info("Attempting non-Slab slab free ...\n");
 kmem_cache_free(NULL, (void *)p);
 free_page(p);
}

void __init lkdtm_heap_init(void)
{
 double_free_cache = kmem_cache_create("lkdtm-heap-double_free",
           64, 0, SLAB_NO_MERGE, NULL);
 a_cache = kmem_cache_create("lkdtm-heap-a", 64, 0, SLAB_NO_MERGE, NULL);
 b_cache = kmem_cache_create("lkdtm-heap-b", 64, 0, SLAB_NO_MERGE, NULL);
}

void __exit lkdtm_heap_exit(void)
{
 kmem_cache_destroy(double_free_cache);
 kmem_cache_destroy(a_cache);
 kmem_cache_destroy(b_cache);
}

static struct crashtype crashtypes[] = {
 CRASHTYPE(SLAB_LINEAR_OVERFLOW),
 CRASHTYPE(VMALLOC_LINEAR_OVERFLOW),
 CRASHTYPE(WRITE_AFTER_FREE),
 CRASHTYPE(READ_AFTER_FREE),
 CRASHTYPE(KFENCE_READ_AFTER_FREE),
 CRASHTYPE(WRITE_BUDDY_AFTER_FREE),
 CRASHTYPE(READ_BUDDY_AFTER_FREE),
 CRASHTYPE(SLAB_INIT_ON_ALLOC),
 CRASHTYPE(BUDDY_INIT_ON_ALLOC),
 CRASHTYPE(SLAB_FREE_DOUBLE),
 CRASHTYPE(SLAB_FREE_CROSS),
 CRASHTYPE(SLAB_FREE_PAGE),
};

struct crashtype_category heap_crashtypes = {
 .crashtypes = crashtypes,
 .len     = ARRAY_SIZE(crashtypes),
};