lib/test_user_copy.c

   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
  36 static 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         /*
  62          * Legitimate usage: none of these copies should fail.
  63          */
  64         ret |= test(copy_from_user(kmem, usermem, PAGE_SIZE),
  65                     "legitimate copy_from_user failed");
  66         ret |= test(copy_to_user(usermem, kmem, PAGE_SIZE),
  67                     "legitimate copy_to_user failed");
  68         ret |= test(get_user(value, (unsigned long __user *)usermem),
  69                     "legitimate get_user failed");
  70         ret |= test(put_user(value, (unsigned long __user *)usermem),
  71                     "legitimate put_user failed");
  72
  73         /*
  74          * Invalid usage: none of these copies should succeed.
  75          */
  76
  77         /* Reject kernel-to-kernel copies through copy_from_user(). */
  78         ret |= test(!copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),
  79                                     PAGE_SIZE),
  80                     "illegal all-kernel copy_from_user passed");
  81
  82 #if 0
  83         /*
  84          * When running with SMAP/PAN/etc, this will Oops the kernel
  85          * due to the zeroing of userspace memory on failure. This needs
  86          * to be tested in LKDTM instead, since this test module does not
  87          * expect to explode.
  88          */
  89         ret |= test(!copy_from_user(bad_usermem, (char __user *)kmem,
  90                                     PAGE_SIZE),
  91                     "illegal reversed copy_from_user passed");
  92 #endif
  93         ret |= test(!copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,
  94                                   PAGE_SIZE),
  95                     "illegal all-kernel copy_to_user passed");
  96         ret |= test(!copy_to_user((char __user *)kmem, bad_usermem,
  97                                   PAGE_SIZE),
  98                     "illegal reversed copy_to_user passed");
  99
 100         ret |= test(!get_user(value, (unsigned long __user *)kmem),
 101                     "illegal get_user passed");
 102         ret |= test(!put_user(value, (unsigned long __user *)kmem),
 103                     "illegal put_user passed");
 104
 105         vm_munmap(user_addr, PAGE_SIZE * 2);
 106         kfree(kmem);
 107
 108         if (ret == 0) {
 109                 pr_info("tests passed.\n");
 110                 return 0;
 111         }
 112
 113         return -EINVAL;
 114 }
 115
 116 module_init(test_user_copy_init);
 117
 118 static void __exit test_user_copy_exit(void)
 119 {
 120         pr_info("unloaded.\n");
 121 }
 122
 123 module_exit(test_user_copy_exit);
 124
 125 MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
 126 MODULE_LICENSE("GPL");