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/*
29 * Several 32-bit architectures support 64-bit {get,put}_user() calls.
30 * As there doesn't appear to be anything that can safely determine
31 * their capability at compile-time, we just have to opt-out certain archs.
32 */
33#if BITS_PER_LONG == 64 || (!(defined(CONFIG_ARM) && !defined(MMU)) && \
34 !defined(CONFIG_M68K) && \
35 !defined(CONFIG_MICROBLAZE) && \
36 !defined(CONFIG_NIOS2) && \
37 !defined(CONFIG_PPC32) && \
38 !defined(CONFIG_SUPERH))
39# define TEST_U64
40#endif
41
42#define test(condition, msg) \
43({ \
44 int cond = (condition); \
45 if (cond) \
46 pr_warn("%s\n", msg); \
47 cond; \
48})
49
50static int __init test_user_copy_init(void)
51{
52 int ret = 0;
53 char *kmem;
54 char __user *usermem;
55 char *bad_usermem;
56 unsigned long user_addr;
57 u8 val_u8;
58 u16 val_u16;
59 u32 val_u32;
60#ifdef TEST_U64
61 u64 val_u64;
62#endif
63
64 kmem = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
65 if (!kmem)
66 return -ENOMEM;
67
68 user_addr = vm_mmap(NULL, 0, PAGE_SIZE * 2,
69 PROT_READ | PROT_WRITE | PROT_EXEC,
70 MAP_ANONYMOUS | MAP_PRIVATE, 0);
71 if (user_addr >= (unsigned long)(TASK_SIZE)) {
72 pr_warn("Failed to allocate user memory\n");
73 kfree(kmem);
74 return -ENOMEM;
75 }
76
77 usermem = (char __user *)user_addr;
78 bad_usermem = (char *)user_addr;
79
80 /*
81 * Legitimate usage: none of these copies should fail.
82 */
83 memset(kmem, 0x3a, PAGE_SIZE * 2);
84 ret |= test(copy_to_user(usermem, kmem, PAGE_SIZE),
85 "legitimate copy_to_user failed");
86 memset(kmem, 0x0, PAGE_SIZE);
87 ret |= test(copy_from_user(kmem, usermem, PAGE_SIZE),
88 "legitimate copy_from_user failed");
89 ret |= test(memcmp(kmem, kmem + PAGE_SIZE, PAGE_SIZE),
90 "legitimate usercopy failed to copy data");
91
92#define test_legit(size, check) \
93 do { \
94 val_##size = check; \
95 ret |= test(put_user(val_##size, (size __user *)usermem), \
96 "legitimate put_user (" #size ") failed"); \
97 val_##size = 0; \
98 ret |= test(get_user(val_##size, (size __user *)usermem), \
99 "legitimate get_user (" #size ") failed"); \
100 ret |= test(val_##size != check, \
101 "legitimate get_user (" #size ") failed to do copy"); \
102 if (val_##size != check) { \
103 pr_info("0x%llx != 0x%llx\n", \
104 (unsigned long long)val_##size, \
105 (unsigned long long)check); \
106 } \
107 } while (0)
108
109 test_legit(u8, 0x5a);
110 test_legit(u16, 0x5a5b);
111 test_legit(u32, 0x5a5b5c5d);
112#ifdef TEST_U64
113 test_legit(u64, 0x5a5b5c5d6a6b6c6d);
114#endif
115#undef test_legit
116
117 /*
118 * Invalid usage: none of these copies should succeed.
119 */
120
121 /* Prepare kernel memory with check values. */
122 memset(kmem, 0x5a, PAGE_SIZE);
123 memset(kmem + PAGE_SIZE, 0, PAGE_SIZE);
124
125 /* Reject kernel-to-kernel copies through copy_from_user(). */
126 ret |= test(!copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),
127 PAGE_SIZE),
128 "illegal all-kernel copy_from_user passed");
129
130 /* Destination half of buffer should have been zeroed. */
131 ret |= test(memcmp(kmem + PAGE_SIZE, kmem, PAGE_SIZE),
132 "zeroing failure for illegal all-kernel copy_from_user");
133
134#if 0
135 /*
136 * When running with SMAP/PAN/etc, this will Oops the kernel
137 * due to the zeroing of userspace memory on failure. This needs
138 * to be tested in LKDTM instead, since this test module does not
139 * expect to explode.
140 */
141 ret |= test(!copy_from_user(bad_usermem, (char __user *)kmem,
142 PAGE_SIZE),
143 "illegal reversed copy_from_user passed");
144#endif
145 ret |= test(!copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,
146 PAGE_SIZE),
147 "illegal all-kernel copy_to_user passed");
148 ret |= test(!copy_to_user((char __user *)kmem, bad_usermem,
149 PAGE_SIZE),
150 "illegal reversed copy_to_user passed");
151
152#define test_illegal(size, check) \
153 do { \
154 val_##size = (check); \
155 ret |= test(!get_user(val_##size, (size __user *)kmem), \
156 "illegal get_user (" #size ") passed"); \
157 ret |= test(val_##size != (size)0, \
158 "zeroing failure for illegal get_user (" #size ")"); \
159 if (val_##size != (size)0) { \
160 pr_info("0x%llx != 0\n", \
161 (unsigned long long)val_##size); \
162 } \
163 ret |= test(!put_user(val_##size, (size __user *)kmem), \
164 "illegal put_user (" #size ") passed"); \
165 } while (0)
166
167 test_illegal(u8, 0x5a);
168 test_illegal(u16, 0x5a5b);
169 test_illegal(u32, 0x5a5b5c5d);
170#ifdef TEST_U64
171 test_illegal(u64, 0x5a5b5c5d6a6b6c6d);
172#endif
173#undef test_illegal
174
175 vm_munmap(user_addr, PAGE_SIZE * 2);
176 kfree(kmem);
177
178 if (ret == 0) {
179 pr_info("tests passed.\n");
180 return 0;
181 }
182
183 return -EINVAL;
184}
185
186module_init(test_user_copy_init);
187
188static void __exit test_user_copy_exit(void)
189{
190 pr_info("unloaded.\n");
191}
192
193module_exit(test_user_copy_exit);
194
195MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
196MODULE_LICENSE("GPL");
197