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Linux/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         /* 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 
100 module_init(test_user_copy_init);
101 
102 static void __exit test_user_copy_exit(void)
103 {
104         pr_info("unloaded.\n");
105 }
106 
107 module_exit(test_user_copy_exit);
108 
109 MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
110 MODULE_LICENSE("GPL");
111 

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