usercopy_kunit.c

  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_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 <kees@kernel.org>");
335MODULE_DESCRIPTION("Kernel module for testing copy_to/from_user infrastructure");
336MODULE_LICENSE("GPL");