1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Kernel module for testing copy_to/from_user infrastructure.
4 *
5 * Copyright 2013 Google Inc. All Rights Reserved
6 *
7 * Authors:
8 * Kees Cook <keescook@chromium.org>
9 */
10
11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12
13 #include <linux/mman.h>
14 #include <linux/module.h>
15 #include <linux/sched.h>
16 #include <linux/slab.h>
17 #include <linux/uaccess.h>
18 #include <kunit/test.h>
19
20 /*
21 * Several 32-bit architectures support 64-bit {get,put}_user() calls.
22 * As there doesn't appear to be anything that can safely determine
23 * their capability at compile-time, we just have to opt-out certain archs.
24 */
25 #if BITS_PER_LONG == 64 || (!(defined(CONFIG_ARM) && !defined(MMU)) && \
26 !defined(CONFIG_M68K) && \
27 !defined(CONFIG_MICROBLAZE) && \
28 !defined(CONFIG_NIOS2) && \
29 !defined(CONFIG_PPC32) && \
30 !defined(CONFIG_SUPERH))
31 # define TEST_U64
32 #endif
33
34 struct usercopy_test_priv {
35 char *kmem;
36 char __user *umem;
37 size_t size;
38 };
39
40 static bool is_zeroed(void *from, size_t size)
41 {
42 return memchr_inv(from, 0x0, size) == NULL;
43 }
44
45 /* Test usage of check_nonzero_user(). */
46 static void usercopy_test_check_nonzero_user(struct kunit *test)
47 {
48 size_t start, end, i, zero_start, zero_end;
49 struct usercopy_test_priv *priv = test->priv;
50 char __user *umem = priv->umem;
51 char *kmem = priv->kmem;
52 size_t size = priv->size;
53
54 KUNIT_ASSERT_GE_MSG(test, size, 2 * PAGE_SIZE, "buffer too small");
55
56 /*
57 * We want to cross a page boundary to exercise the code more
58 * effectively. We also don't want to make the size we scan too large,
59 * otherwise the test can take a long time and cause soft lockups. So
60 * scan a 1024 byte region across the page boundary.
61 */
62 size = 1024;
63 start = PAGE_SIZE - (size / 2);
64
65 kmem += start;
66 umem += start;
67
68 zero_start = size / 4;
69 zero_end = size - zero_start;
70
71 /*
72 * We conduct a series of check_nonzero_user() tests on a block of
73 * memory with the following byte-pattern (trying every possible
74 * [start,end] pair):
75 *
76 * [ 00 ff 00 ff ... 00 00 00 00 ... ff 00 ff 00 ]
77 *
78 * And we verify that check_nonzero_user() acts identically to
79 * memchr_inv().
80 */
81
82 memset(kmem, 0x0, size);
83 for (i = 1; i < zero_start; i += 2)
84 kmem[i] = 0xff;
85 for (i = zero_end; i < size; i += 2)
86 kmem[i] = 0xff;
87
88 KUNIT_EXPECT_EQ_MSG(test, copy_to_user(umem, kmem, size), 0,
89 "legitimate copy_to_user failed");
90
91 for (start = 0; start <= size; start++) {
92 for (end = start; end <= size; end++) {
93 size_t len = end - start;
94 int retval = check_zeroed_user(umem + start, len);
95 int expected = is_zeroed(kmem + start, len);
96
97 KUNIT_ASSERT_EQ_MSG(test, retval, expected,
98 "check_nonzero_user(=%d) != memchr_inv(=%d) mismatch (start=%zu, end=%zu)",
99 retval, expected, start, end);
100 }
101 }
102 }
103
104 /* Test usage of copy_struct_from_user(). */
105 static void usercopy_test_copy_struct_from_user(struct kunit *test)
106 {
107 char *umem_src = NULL, *expected = NULL;
108 struct usercopy_test_priv *priv = test->priv;
109 char __user *umem = priv->umem;
110 char *kmem = priv->kmem;
111 size_t size = priv->size;
112 size_t ksize, usize;
113
114 umem_src = kunit_kmalloc(test, size, GFP_KERNEL);
115 KUNIT_ASSERT_NOT_ERR_OR_NULL(test, umem_src);
116
117 expected = kunit_kmalloc(test, size, GFP_KERNEL);
118 KUNIT_ASSERT_NOT_ERR_OR_NULL(test, expected);
119
120 /* Fill umem with a fixed byte pattern. */
121 memset(umem_src, 0x3e, size);
122 KUNIT_ASSERT_EQ_MSG(test, copy_to_user(umem, umem_src, size), 0,
123 "legitimate copy_to_user failed");
124
125 /* Check basic case -- (usize == ksize). */
126 ksize = size;
127 usize = size;
128
129 memcpy(expected, umem_src, ksize);
130
131 memset(kmem, 0x0, size);
132 KUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), 0,
133 "copy_struct_from_user(usize == ksize) failed");
134 KUNIT_EXPECT_MEMEQ_MSG(test, kmem, expected, ksize,
135 "copy_struct_from_user(usize == ksize) gives unexpected copy");
136
137 /* Old userspace case -- (usize < ksize). */
138 ksize = size;
139 usize = size / 2;
140
141 memcpy(expected, umem_src, usize);
142 memset(expected + usize, 0x0, ksize - usize);
143
144 memset(kmem, 0x0, size);
145 KUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), 0,
146 "copy_struct_from_user(usize < ksize) failed");
147 KUNIT_EXPECT_MEMEQ_MSG(test, kmem, expected, ksize,
148 "copy_struct_from_user(usize < ksize) gives unexpected copy");
149
150 /* New userspace (-E2BIG) case -- (usize > ksize). */
151 ksize = size / 2;
152 usize = size;
153
154 memset(kmem, 0x0, size);
155 KUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), -E2BIG,
156 "copy_struct_from_user(usize > ksize) didn't give E2BIG");
157
158 /* New userspace (success) case -- (usize > ksize). */
159 ksize = size / 2;
160 usize = size;
161
162 memcpy(expected, umem_src, ksize);
163 KUNIT_EXPECT_EQ_MSG(test, clear_user(umem + ksize, usize - ksize), 0,
164 "legitimate clear_user failed");
165
166 memset(kmem, 0x0, size);
167 KUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), 0,
168 "copy_struct_from_user(usize > ksize) failed");
169 KUNIT_EXPECT_MEMEQ_MSG(test, kmem, expected, ksize,
170 "copy_struct_from_user(usize > ksize) gives unexpected copy");
171 }
172
173 /*
174 * Legitimate usage: none of these copies should fail.
175 */
176 static void usercopy_test_valid(struct kunit *test)
177 {
178 struct usercopy_test_priv *priv = test->priv;
179 char __user *usermem = priv->umem;
180 char *kmem = priv->kmem;
181
182 memset(kmem, 0x3a, PAGE_SIZE * 2);
183 KUNIT_EXPECT_EQ_MSG(test, 0, copy_to_user(usermem, kmem, PAGE_SIZE),
184 "legitimate copy_to_user failed");
185 memset(kmem, 0x0, PAGE_SIZE);
186 KUNIT_EXPECT_EQ_MSG(test, 0, copy_from_user(kmem, usermem, PAGE_SIZE),
187 "legitimate copy_from_user failed");
188 KUNIT_EXPECT_MEMEQ_MSG(test, kmem, kmem + PAGE_SIZE, PAGE_SIZE,
189 "legitimate usercopy failed to copy data");
190
191 #define test_legit(size, check) \
192 do { \
193 size val_##size = (check); \
194 KUNIT_EXPECT_EQ_MSG(test, 0, \
195 put_user(val_##size, (size __user *)usermem), \
196 "legitimate put_user (" #size ") failed"); \
197 val_##size = 0; \
198 KUNIT_EXPECT_EQ_MSG(test, 0, \
199 get_user(val_##size, (size __user *)usermem), \
200 "legitimate get_user (" #size ") failed"); \
201 KUNIT_EXPECT_EQ_MSG(test, val_##size, check, \
202 "legitimate get_user (" #size ") failed to do copy"); \
203 } while (0)
204
205 test_legit(u8, 0x5a);
206 test_legit(u16, 0x5a5b);
207 test_legit(u32, 0x5a5b5c5d);
208 #ifdef TEST_U64
209 test_legit(u64, 0x5a5b5c5d6a6b6c6d);
210 #endif
211 #undef test_legit
212 }
213
214 /*
215 * Invalid usage: none of these copies should succeed.
216 */
217 static void usercopy_test_invalid(struct kunit *test)
218 {
219 struct usercopy_test_priv *priv = test->priv;
220 char __user *usermem = priv->umem;
221 char *bad_usermem = (char *)usermem;
222 char *kmem = priv->kmem;
223 u64 *kmem_u64 = (u64 *)kmem;
224
225 if (IS_ENABLED(CONFIG_ALTERNATE_USER_ADDRESS_SPACE) ||
226 !IS_ENABLED(CONFIG_MMU)) {
227 kunit_skip(test, "Testing for kernel/userspace address confusion is only sensible on architectures with a shared address space");
228 return;
229 }
230
231 /* Prepare kernel memory with check values. */
232 memset(kmem, 0x5a, PAGE_SIZE);
233 memset(kmem + PAGE_SIZE, 0, PAGE_SIZE);
234
235 /* Reject kernel-to-kernel copies through copy_from_user(). */
236 KUNIT_EXPECT_NE_MSG(test, copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),
237 PAGE_SIZE), 0,
238 "illegal all-kernel copy_from_user passed");
239
240 /* Destination half of buffer should have been zeroed. */
241 KUNIT_EXPECT_MEMEQ_MSG(test, kmem + PAGE_SIZE, kmem, PAGE_SIZE,
242 "zeroing failure for illegal all-kernel copy_from_user");
243
244 #if 0
245 /*
246 * When running with SMAP/PAN/etc, this will Oops the kernel
247 * due to the zeroing of userspace memory on failure. This needs
248 * to be tested in LKDTM instead, since this test module does not
249 * expect to explode.
250 */
251 KUNIT_EXPECT_NE_MSG(test, copy_from_user(bad_usermem, (char __user *)kmem,
252 PAGE_SIZE), 0,
253 "illegal reversed copy_from_user passed");
254 #endif
255 KUNIT_EXPECT_NE_MSG(test, copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,
256 PAGE_SIZE), 0,
257 "illegal all-kernel copy_to_user passed");
258
259 KUNIT_EXPECT_NE_MSG(test, copy_to_user((char __user *)kmem, bad_usermem,
260 PAGE_SIZE), 0,
261 "illegal reversed copy_to_user passed");
262
263 #define test_illegal(size, check) \
264 do { \
265 size val_##size = (check); \
266 /* get_user() */ \
267 KUNIT_EXPECT_NE_MSG(test, get_user(val_##size, (size __user *)kmem), 0, \
268 "illegal get_user (" #size ") passed"); \
269 KUNIT_EXPECT_EQ_MSG(test, val_##size, 0, \
270 "zeroing failure for illegal get_user (" #size ")"); \
271 /* put_user() */ \
272 *kmem_u64 = 0xF09FA4AFF09FA4AF; \
273 KUNIT_EXPECT_NE_MSG(test, put_user(val_##size, (size __user *)kmem), 0, \
274 "illegal put_user (" #size ") passed"); \
275 KUNIT_EXPECT_EQ_MSG(test, *kmem_u64, 0xF09FA4AFF09FA4AF, \
276 "illegal put_user (" #size ") wrote to kernel memory!"); \
277 } while (0)
278
279 test_illegal(u8, 0x5a);
280 test_illegal(u16, 0x5a5b);
281 test_illegal(u32, 0x5a5b5c5d);
282 #ifdef TEST_U64
283 test_illegal(u64, 0x5a5b5c5d6a6b6c6d);
284 #endif
285 #undef test_illegal
286 }
287
288 static int usercopy_test_init(struct kunit *test)
289 {
290 struct usercopy_test_priv *priv;
291 unsigned long user_addr;
292
293 if (!IS_ENABLED(CONFIG_MMU)) {
294 kunit_skip(test, "Userspace allocation testing not available on non-MMU systems");
295 return 0;
296 }
297
298 priv = kunit_kzalloc(test, sizeof(*priv), GFP_KERNEL);
299 KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv);
300 test->priv = priv;
301 priv->size = PAGE_SIZE * 2;
302
303 priv->kmem = kunit_kmalloc(test, priv->size, GFP_KERNEL);
304 KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv->kmem);
305
306 user_addr = kunit_vm_mmap(test, NULL, 0, priv->size,
307 PROT_READ | PROT_WRITE | PROT_EXEC,
308 MAP_ANONYMOUS | MAP_PRIVATE, 0);
309 KUNIT_ASSERT_NE_MSG(test, user_addr, 0,
310 "Could not create userspace mm");
311 KUNIT_ASSERT_LT_MSG(test, user_addr, (unsigned long)TASK_SIZE,
312 "Failed to allocate user memory");
313 priv->umem = (char __user *)user_addr;
314
315 return 0;
316 }
317
318 static struct kunit_case usercopy_test_cases[] = {
319 KUNIT_CASE(usercopy_test_valid),
320 KUNIT_CASE(usercopy_test_invalid),
321 KUNIT_CASE(usercopy_test_check_nonzero_user),
322 KUNIT_CASE(usercopy_test_copy_struct_from_user),
323 {}
324 };
325
326 static struct kunit_suite usercopy_test_suite = {
327 .name = "usercopy",
328 .init = usercopy_test_init,
329 .test_cases = usercopy_test_cases,
330 };
331
332 kunit_test_suites(&usercopy_test_suite);
333 MODULE_AUTHOR("Kees Cook <kees@kernel.org>");
334 MODULE_DESCRIPTION("Kernel module for testing copy_to/from_user infrastructure");
335 MODULE_LICENSE("GPL");
336
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