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 <linux/vmalloc.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 #define test(condition, msg, ...)					\
35 ({									\
36 	int cond = (condition);						\
37 	if (cond)							\
38 		pr_warn("[%d] " msg "\n", __LINE__, ##__VA_ARGS__);	\
39 	cond;								\
40 })
41 
is_zeroed(void * from,size_t size)42 static bool is_zeroed(void *from, size_t size)
43 {
44 	return memchr_inv(from, 0x0, size) == NULL;
45 }
46 
test_check_nonzero_user(char * kmem,char __user * umem,size_t size)47 static int test_check_nonzero_user(char *kmem, char __user *umem, size_t size)
48 {
49 	int ret = 0;
50 	size_t start, end, i, zero_start, zero_end;
51 
52 	if (test(size < 2 * PAGE_SIZE, "buffer too small"))
53 		return -EINVAL;
54 
55 	/*
56 	 * We want to cross a page boundary to exercise the code more
57 	 * effectively. We also don't want to make the size we scan too large,
58 	 * otherwise the test can take a long time and cause soft lockups. So
59 	 * scan a 1024 byte region across the page boundary.
60 	 */
61 	size = 1024;
62 	start = PAGE_SIZE - (size / 2);
63 
64 	kmem += start;
65 	umem += start;
66 
67 	zero_start = size / 4;
68 	zero_end = size - zero_start;
69 
70 	/*
71 	 * We conduct a series of check_nonzero_user() tests on a block of
72 	 * memory with the following byte-pattern (trying every possible
73 	 * [start,end] pair):
74 	 *
75 	 *   [ 00 ff 00 ff ... 00 00 00 00 ... ff 00 ff 00 ]
76 	 *
77 	 * And we verify that check_nonzero_user() acts identically to
78 	 * memchr_inv().
79 	 */
80 
81 	memset(kmem, 0x0, size);
82 	for (i = 1; i < zero_start; i += 2)
83 		kmem[i] = 0xff;
84 	for (i = zero_end; i < size; i += 2)
85 		kmem[i] = 0xff;
86 
87 	ret |= test(copy_to_user(umem, kmem, size),
88 		    "legitimate copy_to_user failed");
89 
90 	for (start = 0; start <= size; start++) {
91 		for (end = start; end <= size; end++) {
92 			size_t len = end - start;
93 			int retval = check_zeroed_user(umem + start, len);
94 			int expected = is_zeroed(kmem + start, len);
95 
96 			ret |= test(retval != expected,
97 				    "check_nonzero_user(=%d) != memchr_inv(=%d) mismatch (start=%zu, end=%zu)",
98 				    retval, expected, start, end);
99 		}
100 	}
101 
102 	return ret;
103 }
104 
test_copy_struct_from_user(char * kmem,char __user * umem,size_t size)105 static int test_copy_struct_from_user(char *kmem, char __user *umem,
106 				      size_t size)
107 {
108 	int ret = 0;
109 	char *umem_src = NULL, *expected = NULL;
110 	size_t ksize, usize;
111 
112 	umem_src = kmalloc(size, GFP_KERNEL);
113 	ret = test(umem_src == NULL, "kmalloc failed");
114 	if (ret)
115 		goto out_free;
116 
117 	expected = kmalloc(size, GFP_KERNEL);
118 	ret = test(expected == NULL, "kmalloc failed");
119 	if (ret)
120 		goto out_free;
121 
122 	/* Fill umem with a fixed byte pattern. */
123 	memset(umem_src, 0x3e, size);
124 	ret |= test(copy_to_user(umem, umem_src, size),
125 		    "legitimate copy_to_user failed");
126 
127 	/* Check basic case -- (usize == ksize). */
128 	ksize = size;
129 	usize = size;
130 
131 	memcpy(expected, umem_src, ksize);
132 
133 	memset(kmem, 0x0, size);
134 	ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),
135 		    "copy_struct_from_user(usize == ksize) failed");
136 	ret |= test(memcmp(kmem, expected, ksize),
137 		    "copy_struct_from_user(usize == ksize) gives unexpected copy");
138 
139 	/* Old userspace case -- (usize < ksize). */
140 	ksize = size;
141 	usize = size / 2;
142 
143 	memcpy(expected, umem_src, usize);
144 	memset(expected + usize, 0x0, ksize - usize);
145 
146 	memset(kmem, 0x0, size);
147 	ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),
148 		    "copy_struct_from_user(usize < ksize) failed");
149 	ret |= test(memcmp(kmem, expected, ksize),
150 		    "copy_struct_from_user(usize < ksize) gives unexpected copy");
151 
152 	/* New userspace (-E2BIG) case -- (usize > ksize). */
153 	ksize = size / 2;
154 	usize = size;
155 
156 	memset(kmem, 0x0, size);
157 	ret |= test(copy_struct_from_user(kmem, ksize, umem, usize) != -E2BIG,
158 		    "copy_struct_from_user(usize > ksize) didn't give E2BIG");
159 
160 	/* New userspace (success) case -- (usize > ksize). */
161 	ksize = size / 2;
162 	usize = size;
163 
164 	memcpy(expected, umem_src, ksize);
165 	ret |= test(clear_user(umem + ksize, usize - ksize),
166 		    "legitimate clear_user failed");
167 
168 	memset(kmem, 0x0, size);
169 	ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),
170 		    "copy_struct_from_user(usize > ksize) failed");
171 	ret |= test(memcmp(kmem, expected, ksize),
172 		    "copy_struct_from_user(usize > ksize) gives unexpected copy");
173 
174 out_free:
175 	kfree(expected);
176 	kfree(umem_src);
177 	return ret;
178 }
179 
test_user_copy_init(void)180 static int __init test_user_copy_init(void)
181 {
182 	int ret = 0;
183 	char *kmem;
184 	char __user *usermem;
185 	char *bad_usermem;
186 	unsigned long user_addr;
187 	u8 val_u8;
188 	u16 val_u16;
189 	u32 val_u32;
190 #ifdef TEST_U64
191 	u64 val_u64;
192 #endif
193 
194 	kmem = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
195 	if (!kmem)
196 		return -ENOMEM;
197 
198 	user_addr = vm_mmap(NULL, 0, PAGE_SIZE * 2,
199 			    PROT_READ | PROT_WRITE | PROT_EXEC,
200 			    MAP_ANONYMOUS | MAP_PRIVATE, 0);
201 	if (user_addr >= (unsigned long)(TASK_SIZE)) {
202 		pr_warn("Failed to allocate user memory\n");
203 		kfree(kmem);
204 		return -ENOMEM;
205 	}
206 
207 	usermem = (char __user *)user_addr;
208 	bad_usermem = (char *)user_addr;
209 
210 	/*
211 	 * Legitimate usage: none of these copies should fail.
212 	 */
213 	memset(kmem, 0x3a, PAGE_SIZE * 2);
214 	ret |= test(copy_to_user(usermem, kmem, PAGE_SIZE),
215 		    "legitimate copy_to_user failed");
216 	memset(kmem, 0x0, PAGE_SIZE);
217 	ret |= test(copy_from_user(kmem, usermem, PAGE_SIZE),
218 		    "legitimate copy_from_user failed");
219 	ret |= test(memcmp(kmem, kmem + PAGE_SIZE, PAGE_SIZE),
220 		    "legitimate usercopy failed to copy data");
221 
222 #define test_legit(size, check)						  \
223 	do {								  \
224 		val_##size = check;					  \
225 		ret |= test(put_user(val_##size, (size __user *)usermem), \
226 		    "legitimate put_user (" #size ") failed");		  \
227 		val_##size = 0;						  \
228 		ret |= test(get_user(val_##size, (size __user *)usermem), \
229 		    "legitimate get_user (" #size ") failed");		  \
230 		ret |= test(val_##size != check,			  \
231 		    "legitimate get_user (" #size ") failed to do copy"); \
232 		if (val_##size != check) {				  \
233 			pr_info("0x%llx != 0x%llx\n",			  \
234 				(unsigned long long)val_##size,		  \
235 				(unsigned long long)check);		  \
236 		}							  \
237 	} while (0)
238 
239 	test_legit(u8,  0x5a);
240 	test_legit(u16, 0x5a5b);
241 	test_legit(u32, 0x5a5b5c5d);
242 #ifdef TEST_U64
243 	test_legit(u64, 0x5a5b5c5d6a6b6c6d);
244 #endif
245 #undef test_legit
246 
247 	/* Test usage of check_nonzero_user(). */
248 	ret |= test_check_nonzero_user(kmem, usermem, 2 * PAGE_SIZE);
249 	/* Test usage of copy_struct_from_user(). */
250 	ret |= test_copy_struct_from_user(kmem, usermem, 2 * PAGE_SIZE);
251 
252 	/*
253 	 * Invalid usage: none of these copies should succeed.
254 	 */
255 
256 	/* Prepare kernel memory with check values. */
257 	memset(kmem, 0x5a, PAGE_SIZE);
258 	memset(kmem + PAGE_SIZE, 0, PAGE_SIZE);
259 
260 	/* Reject kernel-to-kernel copies through copy_from_user(). */
261 	ret |= test(!copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),
262 				    PAGE_SIZE),
263 		    "illegal all-kernel copy_from_user passed");
264 
265 	/* Destination half of buffer should have been zeroed. */
266 	ret |= test(memcmp(kmem + PAGE_SIZE, kmem, PAGE_SIZE),
267 		    "zeroing failure for illegal all-kernel copy_from_user");
268 
269 #if 0
270 	/*
271 	 * When running with SMAP/PAN/etc, this will Oops the kernel
272 	 * due to the zeroing of userspace memory on failure. This needs
273 	 * to be tested in LKDTM instead, since this test module does not
274 	 * expect to explode.
275 	 */
276 	ret |= test(!copy_from_user(bad_usermem, (char __user *)kmem,
277 				    PAGE_SIZE),
278 		    "illegal reversed copy_from_user passed");
279 #endif
280 	ret |= test(!copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,
281 				  PAGE_SIZE),
282 		    "illegal all-kernel copy_to_user passed");
283 	ret |= test(!copy_to_user((char __user *)kmem, bad_usermem,
284 				  PAGE_SIZE),
285 		    "illegal reversed copy_to_user passed");
286 
287 #define test_illegal(size, check)					    \
288 	do {								    \
289 		val_##size = (check);					    \
290 		ret |= test(!get_user(val_##size, (size __user *)kmem),	    \
291 		    "illegal get_user (" #size ") passed");		    \
292 		ret |= test(val_##size != (size)0,			    \
293 		    "zeroing failure for illegal get_user (" #size ")");    \
294 		if (val_##size != (size)0) {				    \
295 			pr_info("0x%llx != 0\n",			    \
296 				(unsigned long long)val_##size);	    \
297 		}							    \
298 		ret |= test(!put_user(val_##size, (size __user *)kmem),	    \
299 		    "illegal put_user (" #size ") passed");		    \
300 	} while (0)
301 
302 	test_illegal(u8,  0x5a);
303 	test_illegal(u16, 0x5a5b);
304 	test_illegal(u32, 0x5a5b5c5d);
305 #ifdef TEST_U64
306 	test_illegal(u64, 0x5a5b5c5d6a6b6c6d);
307 #endif
308 #undef test_illegal
309 
310 	vm_munmap(user_addr, PAGE_SIZE * 2);
311 	kfree(kmem);
312 
313 	if (ret == 0) {
314 		pr_info("tests passed.\n");
315 		return 0;
316 	}
317 
318 	return -EINVAL;
319 }
320 
321 module_init(test_user_copy_init);
322 
test_user_copy_exit(void)323 static void __exit test_user_copy_exit(void)
324 {
325 	pr_info("unloaded.\n");
326 }
327 
328 module_exit(test_user_copy_exit);
329 
330 MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
331 MODULE_LICENSE("GPL");
332