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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 <[email protected]>
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_SPARC32) && \
31 !defined(CONFIG_SUPERH))
32# define TEST_U64
33#endif
34
35struct usercopy_test_priv {
36 char *kmem;
37 char __user *umem;
38 size_t size;
39};
40
41static bool is_zeroed(void *from, size_t size)
42{
43 return memchr_inv(from, 0x0, size) == NULL;
44}
45
46/* Test usage of check_nonzero_user(). */
47static void usercopy_test_check_nonzero_user(struct kunit *test)
48{
49 size_t start, end, i, zero_start, zero_end;
50 struct usercopy_test_priv *priv = test->priv;
51 char __user *umem = priv->umem;
52 char *kmem = priv->kmem;
53 size_t size = priv->size;
54
55 KUNIT_ASSERT_GE_MSG(test, size, 2 * PAGE_SIZE, "buffer too small");
56
57 /*
58 * We want to cross a page boundary to exercise the code more
59 * effectively. We also don't want to make the size we scan too large,
60 * otherwise the test can take a long time and cause soft lockups. So
61 * scan a 1024 byte region across the page boundary.
62 */
63 size = 1024;
64 start = PAGE_SIZE - (size / 2);
65
66 kmem += start;
67 umem += start;
68
69 zero_start = size / 4;
70 zero_end = size - zero_start;
71
72 /*
73 * We conduct a series of check_nonzero_user() tests on a block of
74 * memory with the following byte-pattern (trying every possible
75 * [start,end] pair):
76 *
77 * [ 00 ff 00 ff ... 00 00 00 00 ... ff 00 ff 00 ]
78 *
79 * And we verify that check_nonzero_user() acts identically to
80 * memchr_inv().
81 */
82
83 memset(kmem, 0x0, size);
84 for (i = 1; i < zero_start; i += 2)
85 kmem[i] = 0xff;
86 for (i = zero_end; i < size; i += 2)
87 kmem[i] = 0xff;
88
89 KUNIT_EXPECT_EQ_MSG(test, copy_to_user(umem, kmem, size), 0,
90 "legitimate copy_to_user failed");
91
92 for (start = 0; start <= size; start++) {
93 for (end = start; end <= size; end++) {
94 size_t len = end - start;
95 int retval = check_zeroed_user(umem + start, len);
96 int expected = is_zeroed(kmem + start, len);
97
98 KUNIT_ASSERT_EQ_MSG(test, retval, expected,
99 "check_nonzero_user(=%d) != memchr_inv(=%d) mismatch (start=%zu, end=%zu)",
100 retval, expected, start, end);
101 }
102 }
103}
104
105/* Test usage of copy_struct_from_user(). */
106static void usercopy_test_copy_struct_from_user(struct kunit *test)
107{
108 char *umem_src = NULL, *expected = NULL;
109 struct usercopy_test_priv *priv = test->priv;
110 char __user *umem = priv->umem;
111 char *kmem = priv->kmem;
112 size_t size = priv->size;
113 size_t ksize, usize;
114
115 umem_src = kunit_kmalloc(test, size, GFP_KERNEL);
116 KUNIT_ASSERT_NOT_ERR_OR_NULL(test, umem_src);
117
118 expected = kunit_kmalloc(test, size, GFP_KERNEL);
119 KUNIT_ASSERT_NOT_ERR_OR_NULL(test, expected);
120
121 /* Fill umem with a fixed byte pattern. */
122 memset(umem_src, 0x3e, size);
123 KUNIT_ASSERT_EQ_MSG(test, copy_to_user(umem, umem_src, size), 0,
124 "legitimate copy_to_user failed");
125
126 /* Check basic case -- (usize == ksize). */
127 ksize = size;
128 usize = size;
129
130 memcpy(expected, umem_src, ksize);
131
132 memset(kmem, 0x0, size);
133 KUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), 0,
134 "copy_struct_from_user(usize == ksize) failed");
135 KUNIT_EXPECT_MEMEQ_MSG(test, kmem, expected, ksize,
136 "copy_struct_from_user(usize == ksize) gives unexpected copy");
137
138 /* Old userspace case -- (usize < ksize). */
139 ksize = size;
140 usize = size / 2;
141
142 memcpy(expected, umem_src, usize);
143 memset(expected + usize, 0x0, ksize - usize);
144
145 memset(kmem, 0x0, size);
146 KUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), 0,
147 "copy_struct_from_user(usize < ksize) failed");
148 KUNIT_EXPECT_MEMEQ_MSG(test, kmem, expected, ksize,
149 "copy_struct_from_user(usize < ksize) gives unexpected copy");
150
151 /* New userspace (-E2BIG) case -- (usize > ksize). */
152 ksize = size / 2;
153 usize = size;
154
155 memset(kmem, 0x0, size);
156 KUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), -E2BIG,
157 "copy_struct_from_user(usize > ksize) didn't give E2BIG");
158
159 /* New userspace (success) case -- (usize > ksize). */
160 ksize = size / 2;
161 usize = size;
162
163 memcpy(expected, umem_src, ksize);
164 KUNIT_EXPECT_EQ_MSG(test, clear_user(umem + ksize, usize - ksize), 0,
165 "legitimate clear_user failed");
166
167 memset(kmem, 0x0, size);
168 KUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), 0,
169 "copy_struct_from_user(usize > ksize) failed");
170 KUNIT_EXPECT_MEMEQ_MSG(test, kmem, expected, ksize,
171 "copy_struct_from_user(usize > ksize) gives unexpected copy");
172}
173
174/*
175 * Legitimate usage: none of these copies should fail.
176 */
177static void usercopy_test_valid(struct kunit *test)
178{
179 struct usercopy_test_priv *priv = test->priv;
180 char __user *usermem = priv->umem;
181 char *kmem = priv->kmem;
182
183 memset(kmem, 0x3a, PAGE_SIZE * 2);
184 KUNIT_EXPECT_EQ_MSG(test, 0, copy_to_user(usermem, kmem, PAGE_SIZE),
185 "legitimate copy_to_user failed");
186 memset(kmem, 0x0, PAGE_SIZE);
187 KUNIT_EXPECT_EQ_MSG(test, 0, copy_from_user(kmem, usermem, PAGE_SIZE),
188 "legitimate copy_from_user failed");
189 KUNIT_EXPECT_MEMEQ_MSG(test, kmem, kmem + PAGE_SIZE, PAGE_SIZE,
190 "legitimate usercopy failed to copy data");
191
192#define test_legit(size, check) \
193 do { \
194 size val_##size = (check); \
195 KUNIT_EXPECT_EQ_MSG(test, 0, \
196 put_user(val_##size, (size __user *)usermem), \
197 "legitimate put_user (" #size ") failed"); \
198 val_##size = 0; \
199 KUNIT_EXPECT_EQ_MSG(test, 0, \
200 get_user(val_##size, (size __user *)usermem), \
201 "legitimate get_user (" #size ") failed"); \
202 KUNIT_EXPECT_EQ_MSG(test, val_##size, check, \
203 "legitimate get_user (" #size ") failed to do copy"); \
204 } while (0)
205
206 test_legit(u8, 0x5a);
207 test_legit(u16, 0x5a5b);
208 test_legit(u32, 0x5a5b5c5d);
209#ifdef TEST_U64
210 test_legit(u64, 0x5a5b5c5d6a6b6c6d);
211#endif
212#undef test_legit
213}
214
215/*
216 * Invalid usage: none of these copies should succeed.
217 */
218static void usercopy_test_invalid(struct kunit *test)
219{
220 struct usercopy_test_priv *priv = test->priv;
221 char __user *usermem = priv->umem;
222 char *bad_usermem = (char *)usermem;
223 char *kmem = priv->kmem;
224 u64 *kmem_u64 = (u64 *)kmem;
225
226 if (IS_ENABLED(CONFIG_ALTERNATE_USER_ADDRESS_SPACE) ||
227 !IS_ENABLED(CONFIG_MMU)) {
228 kunit_skip(test, "Testing for kernel/userspace address confusion is only sensible on architectures with a shared address space");
229 return;
230 }
231
232 /* Prepare kernel memory with check values. */
233 memset(kmem, 0x5a, PAGE_SIZE);
234 memset(kmem + PAGE_SIZE, 0, PAGE_SIZE);
235
236 /* Reject kernel-to-kernel copies through copy_from_user(). */
237 KUNIT_EXPECT_NE_MSG(test, copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),
238 PAGE_SIZE), 0,
239 "illegal all-kernel copy_from_user passed");
240
241 /* Destination half of buffer should have been zeroed. */
242 KUNIT_EXPECT_MEMEQ_MSG(test, kmem + PAGE_SIZE, kmem, PAGE_SIZE,
243 "zeroing failure for illegal all-kernel copy_from_user");
244
245#if 0
246 /*
247 * When running with SMAP/PAN/etc, this will Oops the kernel
248 * due to the zeroing of userspace memory on failure. This needs
249 * to be tested in LKDTM instead, since this test module does not
250 * expect to explode.
251 */
252 KUNIT_EXPECT_NE_MSG(test, copy_from_user(bad_usermem, (char __user *)kmem,
253 PAGE_SIZE), 0,
254 "illegal reversed copy_from_user passed");
255#endif
256 KUNIT_EXPECT_NE_MSG(test, copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,
257 PAGE_SIZE), 0,
258 "illegal all-kernel copy_to_user passed");
259
260 KUNIT_EXPECT_NE_MSG(test, copy_to_user((char __user *)kmem, bad_usermem,
261 PAGE_SIZE), 0,
262 "illegal reversed copy_to_user passed");
263
264#define test_illegal(size, check) \
265 do { \
266 size val_##size = (check); \
267 /* get_user() */ \
268 KUNIT_EXPECT_NE_MSG(test, get_user(val_##size, (size __user *)kmem), 0, \
269 "illegal get_user (" #size ") passed"); \
270 KUNIT_EXPECT_EQ_MSG(test, val_##size, 0, \
271 "zeroing failure for illegal get_user (" #size ")"); \
272 /* put_user() */ \
273 *kmem_u64 = 0xF09FA4AFF09FA4AF; \
274 KUNIT_EXPECT_NE_MSG(test, put_user(val_##size, (size __user *)kmem), 0, \
275 "illegal put_user (" #size ") passed"); \
276 KUNIT_EXPECT_EQ_MSG(test, *kmem_u64, 0xF09FA4AFF09FA4AF, \
277 "illegal put_user (" #size ") wrote to kernel memory!"); \
278 } while (0)
279
280 test_illegal(u8, 0x5a);
281 test_illegal(u16, 0x5a5b);
282 test_illegal(u32, 0x5a5b5c5d);
283#ifdef TEST_U64
284 test_illegal(u64, 0x5a5b5c5d6a6b6c6d);
285#endif
286#undef test_illegal
287}
288
289static int usercopy_test_init(struct kunit *test)
290{
291 struct usercopy_test_priv *priv;
292 unsigned long user_addr;
293
294 if (!IS_ENABLED(CONFIG_MMU)) {
295 kunit_skip(test, "Userspace allocation testing not available on non-MMU systems");
296 return 0;
297 }
298
299 priv = kunit_kzalloc(test, sizeof(*priv), GFP_KERNEL);
300 KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv);
301 test->priv = priv;
302 priv->size = PAGE_SIZE * 2;
303
304 priv->kmem = kunit_kmalloc(test, priv->size, GFP_KERNEL);
305 KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv->kmem);
306
307 user_addr = kunit_vm_mmap(test, NULL, 0, priv->size,
308 PROT_READ | PROT_WRITE | PROT_EXEC,
309 MAP_ANONYMOUS | MAP_PRIVATE, 0);
310 KUNIT_ASSERT_NE_MSG(test, user_addr, 0,
311 "Could not create userspace mm");
312 KUNIT_ASSERT_LT_MSG(test, user_addr, (unsigned long)TASK_SIZE,
313 "Failed to allocate user memory");
314 priv->umem = (char __user *)user_addr;
315
316 return 0;
317}
318
319static struct kunit_case usercopy_test_cases[] = {
320 KUNIT_CASE(usercopy_test_valid),
321 KUNIT_CASE(usercopy_test_invalid),
322 KUNIT_CASE(usercopy_test_check_nonzero_user),
323 KUNIT_CASE(usercopy_test_copy_struct_from_user),
324 {}
325};
326
327static struct kunit_suite usercopy_test_suite = {
328 .name = "usercopy",
329 .init = usercopy_test_init,
330 .test_cases = usercopy_test_cases,
331};
332
333kunit_test_suites(&usercopy_test_suite);
334MODULE_AUTHOR("Kees Cook <[email protected]>");
335MODULE_DESCRIPTION("Kernel module for testing copy_to/from_user infrastructure");
336MODULE_LICENSE("GPL");