linux/lib/test_user_copy.c
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   1/*
   2 * Kernel module for testing copy_to/from_user infrastructure.
   3 *
   4 * Copyright 2013 Google Inc. All Rights Reserved
   5 *
   6 * Authors:
   7 *      Kees Cook       <keescook@chromium.org>
   8 *
   9 * This software is licensed under the terms of the GNU General Public
  10 * License version 2, as published by the Free Software Foundation, and
  11 * may be copied, distributed, and modified under those terms.
  12 *
  13 * This program is distributed in the hope that it will be useful,
  14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 * GNU General Public License for more details.
  17 */
  18
  19#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  20
  21#include <linux/mman.h>
  22#include <linux/module.h>
  23#include <linux/sched.h>
  24#include <linux/slab.h>
  25#include <linux/uaccess.h>
  26#include <linux/vmalloc.h>
  27
  28#define test(condition, msg)            \
  29({                                      \
  30        int cond = (condition);         \
  31        if (cond)                       \
  32                pr_warn("%s\n", msg);   \
  33        cond;                           \
  34})
  35
  36static int __init test_user_copy_init(void)
  37{
  38        int ret = 0;
  39        char *kmem;
  40        char __user *usermem;
  41        char *bad_usermem;
  42        unsigned long user_addr;
  43        unsigned long value = 0x5A;
  44
  45        kmem = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
  46        if (!kmem)
  47                return -ENOMEM;
  48
  49        user_addr = vm_mmap(NULL, 0, PAGE_SIZE * 2,
  50                            PROT_READ | PROT_WRITE | PROT_EXEC,
  51                            MAP_ANONYMOUS | MAP_PRIVATE, 0);
  52        if (user_addr >= (unsigned long)(TASK_SIZE)) {
  53                pr_warn("Failed to allocate user memory\n");
  54                kfree(kmem);
  55                return -ENOMEM;
  56        }
  57
  58        usermem = (char __user *)user_addr;
  59        bad_usermem = (char *)user_addr;
  60
  61        /* Legitimate usage: none of these should fail. */
  62        ret |= test(copy_from_user(kmem, usermem, PAGE_SIZE),
  63                    "legitimate copy_from_user failed");
  64        ret |= test(copy_to_user(usermem, kmem, PAGE_SIZE),
  65                    "legitimate copy_to_user failed");
  66        ret |= test(get_user(value, (unsigned long __user *)usermem),
  67                    "legitimate get_user failed");
  68        ret |= test(put_user(value, (unsigned long __user *)usermem),
  69                    "legitimate put_user failed");
  70
  71        /* Invalid usage: none of these should succeed. */
  72        ret |= test(!copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),
  73                                    PAGE_SIZE),
  74                    "illegal all-kernel copy_from_user passed");
  75        ret |= test(!copy_from_user(bad_usermem, (char __user *)kmem,
  76                                    PAGE_SIZE),
  77                    "illegal reversed copy_from_user passed");
  78        ret |= test(!copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,
  79                                  PAGE_SIZE),
  80                    "illegal all-kernel copy_to_user passed");
  81        ret |= test(!copy_to_user((char __user *)kmem, bad_usermem,
  82                                  PAGE_SIZE),
  83                    "illegal reversed copy_to_user passed");
  84        ret |= test(!get_user(value, (unsigned long __user *)kmem),
  85                    "illegal get_user passed");
  86        ret |= test(!put_user(value, (unsigned long __user *)kmem),
  87                    "illegal put_user passed");
  88
  89        vm_munmap(user_addr, PAGE_SIZE * 2);
  90        kfree(kmem);
  91
  92        if (ret == 0) {
  93                pr_info("tests passed.\n");
  94                return 0;
  95        }
  96
  97        return -EINVAL;
  98}
  99
 100module_init(test_user_copy_init);
 101
 102static void __exit test_user_copy_exit(void)
 103{
 104        pr_info("unloaded.\n");
 105}
 106
 107module_exit(test_user_copy_exit);
 108
 109MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
 110MODULE_LICENSE("GPL");
 111