1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Access kernel or user memory without faulting.
4 */
5#include <linux/export.h>
6#include <linux/mm.h>
7#include <linux/uaccess.h>
8#include <asm/tlb.h>
9
10bool __weak copy_from_kernel_nofault_allowed(const void *unsafe_src,
11		size_t size)
12{
13	return true;
14}
15
16#define copy_from_kernel_nofault_loop(dst, src, len, type, err_label)	\
17	while (len >= sizeof(type)) {					\
18		__get_kernel_nofault(dst, src, type, err_label);		\
19		dst += sizeof(type);					\
20		src += sizeof(type);					\
21		len -= sizeof(type);					\
22	}
23
24long copy_from_kernel_nofault(void *dst, const void *src, size_t size)
25{
26	unsigned long align = 0;
27
28	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
29		align = (unsigned long)dst | (unsigned long)src;
30
31	if (!copy_from_kernel_nofault_allowed(src, size))
32		return -ERANGE;
33
34	pagefault_disable();
35	if (!(align & 7))
36		copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
37	if (!(align & 3))
38		copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
39	if (!(align & 1))
40		copy_from_kernel_nofault_loop(dst, src, size, u16, Efault);
41	copy_from_kernel_nofault_loop(dst, src, size, u8, Efault);
42	pagefault_enable();
43	return 0;
44Efault:
45	pagefault_enable();
46	return -EFAULT;
47}
48EXPORT_SYMBOL_GPL(copy_from_kernel_nofault);
49
50#define copy_to_kernel_nofault_loop(dst, src, len, type, err_label)	\
51	while (len >= sizeof(type)) {					\
52		__put_kernel_nofault(dst, src, type, err_label);		\
53		dst += sizeof(type);					\
54		src += sizeof(type);					\
55		len -= sizeof(type);					\
56	}
57
58long copy_to_kernel_nofault(void *dst, const void *src, size_t size)
59{
60	unsigned long align = 0;
61
62	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
63		align = (unsigned long)dst | (unsigned long)src;
64
65	pagefault_disable();
66	if (!(align & 7))
67		copy_to_kernel_nofault_loop(dst, src, size, u64, Efault);
68	if (!(align & 3))
69		copy_to_kernel_nofault_loop(dst, src, size, u32, Efault);
70	if (!(align & 1))
71		copy_to_kernel_nofault_loop(dst, src, size, u16, Efault);
72	copy_to_kernel_nofault_loop(dst, src, size, u8, Efault);
73	pagefault_enable();
74	return 0;
75Efault:
76	pagefault_enable();
77	return -EFAULT;
78}
79
80long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
81{
82	const void *src = unsafe_addr;
83
84	if (unlikely(count <= 0))
85		return 0;
86	if (!copy_from_kernel_nofault_allowed(unsafe_addr, count))
87		return -ERANGE;
88
89	pagefault_disable();
90	do {
91		__get_kernel_nofault(dst, src, u8, Efault);
92		dst++;
93		src++;
94	} while (dst[-1] && src - unsafe_addr < count);
95	pagefault_enable();
96
97	dst[-1] = '\0';
98	return src - unsafe_addr;
99Efault:
100	pagefault_enable();
101	dst[0] = '\0';
102	return -EFAULT;
103}
104
105/**
106 * copy_from_user_nofault(): safely attempt to read from a user-space location
107 * @dst: pointer to the buffer that shall take the data
108 * @src: address to read from. This must be a user address.
109 * @size: size of the data chunk
110 *
111 * Safely read from user address @src to the buffer at @dst. If a kernel fault
112 * happens, handle that and return -EFAULT.
113 */
114long copy_from_user_nofault(void *dst, const void __user *src, size_t size)
115{
116	long ret = -EFAULT;
117
118	if (!__access_ok(src, size))
119		return ret;
120
121	if (!nmi_uaccess_okay())
122		return ret;
123
124	pagefault_disable();
125	ret = __copy_from_user_inatomic(dst, src, size);
126	pagefault_enable();
127
128	if (ret)
129		return -EFAULT;
130	return 0;
131}
132EXPORT_SYMBOL_GPL(copy_from_user_nofault);
133
134/**
135 * copy_to_user_nofault(): safely attempt to write to a user-space location
136 * @dst: address to write to
137 * @src: pointer to the data that shall be written
138 * @size: size of the data chunk
139 *
140 * Safely write to address @dst from the buffer at @src.  If a kernel fault
141 * happens, handle that and return -EFAULT.
142 */
143long copy_to_user_nofault(void __user *dst, const void *src, size_t size)
144{
145	long ret = -EFAULT;
146
147	if (access_ok(dst, size)) {
148		pagefault_disable();
149		ret = __copy_to_user_inatomic(dst, src, size);
150		pagefault_enable();
151	}
152
153	if (ret)
154		return -EFAULT;
155	return 0;
156}
157EXPORT_SYMBOL_GPL(copy_to_user_nofault);
158
159/**
160 * strncpy_from_user_nofault: - Copy a NUL terminated string from unsafe user
161 *				address.
162 * @dst:   Destination address, in kernel space.  This buffer must be at
163 *         least @count bytes long.
164 * @unsafe_addr: Unsafe user address.
165 * @count: Maximum number of bytes to copy, including the trailing NUL.
166 *
167 * Copies a NUL-terminated string from unsafe user address to kernel buffer.
168 *
169 * On success, returns the length of the string INCLUDING the trailing NUL.
170 *
171 * If access fails, returns -EFAULT (some data may have been copied
172 * and the trailing NUL added).
173 *
174 * If @count is smaller than the length of the string, copies @count-1 bytes,
175 * sets the last byte of @dst buffer to NUL and returns @count.
176 */
177long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
178			      long count)
179{
180	long ret;
181
182	if (unlikely(count <= 0))
183		return 0;
184
185	pagefault_disable();
186	ret = strncpy_from_user(dst, unsafe_addr, count);
187	pagefault_enable();
188
189	if (ret >= count) {
190		ret = count;
191		dst[ret - 1] = '\0';
192	} else if (ret > 0) {
193		ret++;
194	}
195
196	return ret;
197}
198
199/**
200 * strnlen_user_nofault: - Get the size of a user string INCLUDING final NUL.
201 * @unsafe_addr: The string to measure.
202 * @count: Maximum count (including NUL)
203 *
204 * Get the size of a NUL-terminated string in user space without pagefault.
205 *
206 * Returns the size of the string INCLUDING the terminating NUL.
207 *
208 * If the string is too long, returns a number larger than @count. User
209 * has to check the return value against "> count".
210 * On exception (or invalid count), returns 0.
211 *
212 * Unlike strnlen_user, this can be used from IRQ handler etc. because
213 * it disables pagefaults.
214 */
215long strnlen_user_nofault(const void __user *unsafe_addr, long count)
216{
217	int ret;
218
219	pagefault_disable();
220	ret = strnlen_user(unsafe_addr, count);
221	pagefault_enable();
222
223	return ret;
224}
225
226void __copy_overflow(int size, unsigned long count)
227{
228	WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count);
229}
230EXPORT_SYMBOL(__copy_overflow);
231