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");