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
42static bool is_zeroed(void *from, size_t size)
43{
44	return memchr_inv(from, 0x0, size) == NULL;
45}
46
47static 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
105static 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
174out_free:
175	kfree(expected);
176	kfree(umem_src);
177	return ret;
178}
179
180static 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
321module_init(test_user_copy_init);
322
323static void __exit test_user_copy_exit(void)
324{
325	pr_info("unloaded.\n");
326}
327
328module_exit(test_user_copy_exit);
329
330MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
331MODULE_LICENSE("GPL");
332