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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
9bool __weak copy_from_kernel_nofault_allowed(const void *unsafe_src,
10 size_t size)
11{
12 return true;
13}
14
15#ifdef HAVE_GET_KERNEL_NOFAULT
16
17#define copy_from_kernel_nofault_loop(dst, src, len, type, err_label) \
18 while (len >= sizeof(type)) { \
19 __get_kernel_nofault(dst, src, type, err_label); \
20 dst += sizeof(type); \
21 src += sizeof(type); \
22 len -= sizeof(type); \
23 }
24
25long copy_from_kernel_nofault(void *dst, const void *src, size_t size)
26{
27 if (!copy_from_kernel_nofault_allowed(src, size))
28 return -ERANGE;
29
30 pagefault_disable();
31 copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
32 copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
33 copy_from_kernel_nofault_loop(dst, src, size, u16, Efault);
34 copy_from_kernel_nofault_loop(dst, src, size, u8, Efault);
35 pagefault_enable();
36 return 0;
37Efault:
38 pagefault_enable();
39 return -EFAULT;
40}
41EXPORT_SYMBOL_GPL(copy_from_kernel_nofault);
42
43#define copy_to_kernel_nofault_loop(dst, src, len, type, err_label) \
44 while (len >= sizeof(type)) { \
45 __put_kernel_nofault(dst, src, type, err_label); \
46 dst += sizeof(type); \
47 src += sizeof(type); \
48 len -= sizeof(type); \
49 }
50
51long copy_to_kernel_nofault(void *dst, const void *src, size_t size)
52{
53 pagefault_disable();
54 copy_to_kernel_nofault_loop(dst, src, size, u64, Efault);
55 copy_to_kernel_nofault_loop(dst, src, size, u32, Efault);
56 copy_to_kernel_nofault_loop(dst, src, size, u16, Efault);
57 copy_to_kernel_nofault_loop(dst, src, size, u8, Efault);
58 pagefault_enable();
59 return 0;
60Efault:
61 pagefault_enable();
62 return -EFAULT;
63}
64
65long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
66{
67 const void *src = unsafe_addr;
68
69 if (unlikely(count <= 0))
70 return 0;
71 if (!copy_from_kernel_nofault_allowed(unsafe_addr, count))
72 return -ERANGE;
73
74 pagefault_disable();
75 do {
76 __get_kernel_nofault(dst, src, u8, Efault);
77 dst++;
78 src++;
79 } while (dst[-1] && src - unsafe_addr < count);
80 pagefault_enable();
81
82 dst[-1] = '\0';
83 return src - unsafe_addr;
84Efault:
85 pagefault_enable();
86 dst[-1] = '\0';
87 return -EFAULT;
88}
89#else /* HAVE_GET_KERNEL_NOFAULT */
90/**
91 * copy_from_kernel_nofault(): safely attempt to read from kernel-space
92 * @dst: pointer to the buffer that shall take the data
93 * @src: address to read from
94 * @size: size of the data chunk
95 *
96 * Safely read from kernel address @src to the buffer at @dst. If a kernel
97 * fault happens, handle that and return -EFAULT. If @src is not a valid kernel
98 * address, return -ERANGE.
99 *
100 * We ensure that the copy_from_user is executed in atomic context so that
101 * do_page_fault() doesn't attempt to take mmap_lock. This makes
102 * copy_from_kernel_nofault() suitable for use within regions where the caller
103 * already holds mmap_lock, or other locks which nest inside mmap_lock.
104 */
105long copy_from_kernel_nofault(void *dst, const void *src, size_t size)
106{
107 long ret;
108 mm_segment_t old_fs = get_fs();
109
110 if (!copy_from_kernel_nofault_allowed(src, size))
111 return -ERANGE;
112
113 set_fs(KERNEL_DS);
114 pagefault_disable();
115 ret = __copy_from_user_inatomic(dst, (__force const void __user *)src,
116 size);
117 pagefault_enable();
118 set_fs(old_fs);
119
120 if (ret)
121 return -EFAULT;
122 return 0;
123}
124EXPORT_SYMBOL_GPL(copy_from_kernel_nofault);
125
126/**
127 * copy_to_kernel_nofault(): safely attempt to write to a location
128 * @dst: address to write to
129 * @src: pointer to the data that shall be written
130 * @size: size of the data chunk
131 *
132 * Safely write to address @dst from the buffer at @src. If a kernel fault
133 * happens, handle that and return -EFAULT.
134 */
135long copy_to_kernel_nofault(void *dst, const void *src, size_t size)
136{
137 long ret;
138 mm_segment_t old_fs = get_fs();
139
140 set_fs(KERNEL_DS);
141 pagefault_disable();
142 ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
143 pagefault_enable();
144 set_fs(old_fs);
145
146 if (ret)
147 return -EFAULT;
148 return 0;
149}
150
151/**
152 * strncpy_from_kernel_nofault: - Copy a NUL terminated string from unsafe
153 * address.
154 * @dst: Destination address, in kernel space. This buffer must be at
155 * least @count bytes long.
156 * @unsafe_addr: Unsafe address.
157 * @count: Maximum number of bytes to copy, including the trailing NUL.
158 *
159 * Copies a NUL-terminated string from unsafe address to kernel buffer.
160 *
161 * On success, returns the length of the string INCLUDING the trailing NUL.
162 *
163 * If access fails, returns -EFAULT (some data may have been copied and the
164 * trailing NUL added). If @unsafe_addr is not a valid kernel address, return
165 * -ERANGE.
166 *
167 * If @count is smaller than the length of the string, copies @count-1 bytes,
168 * sets the last byte of @dst buffer to NUL and returns @count.
169 */
170long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
171{
172 mm_segment_t old_fs = get_fs();
173 const void *src = unsafe_addr;
174 long ret;
175
176 if (unlikely(count <= 0))
177 return 0;
178 if (!copy_from_kernel_nofault_allowed(unsafe_addr, count))
179 return -ERANGE;
180
181 set_fs(KERNEL_DS);
182 pagefault_disable();
183
184 do {
185 ret = __get_user(*dst++, (const char __user __force *)src++);
186 } while (dst[-1] && ret == 0 && src - unsafe_addr < count);
187
188 dst[-1] = '\0';
189 pagefault_enable();
190 set_fs(old_fs);
191
192 return ret ? -EFAULT : src - unsafe_addr;
193}
194#endif /* HAVE_GET_KERNEL_NOFAULT */
195
196/**
197 * copy_from_user_nofault(): safely attempt to read from a user-space location
198 * @dst: pointer to the buffer that shall take the data
199 * @src: address to read from. This must be a user address.
200 * @size: size of the data chunk
201 *
202 * Safely read from user address @src to the buffer at @dst. If a kernel fault
203 * happens, handle that and return -EFAULT.
204 */
205long copy_from_user_nofault(void *dst, const void __user *src, size_t size)
206{
207 long ret = -EFAULT;
208 mm_segment_t old_fs = force_uaccess_begin();
209
210 if (access_ok(src, size)) {
211 pagefault_disable();
212 ret = __copy_from_user_inatomic(dst, src, size);
213 pagefault_enable();
214 }
215 force_uaccess_end(old_fs);
216
217 if (ret)
218 return -EFAULT;
219 return 0;
220}
221EXPORT_SYMBOL_GPL(copy_from_user_nofault);
222
223/**
224 * copy_to_user_nofault(): safely attempt to write to a user-space location
225 * @dst: address to write to
226 * @src: pointer to the data that shall be written
227 * @size: size of the data chunk
228 *
229 * Safely write to address @dst from the buffer at @src. If a kernel fault
230 * happens, handle that and return -EFAULT.
231 */
232long copy_to_user_nofault(void __user *dst, const void *src, size_t size)
233{
234 long ret = -EFAULT;
235 mm_segment_t old_fs = force_uaccess_begin();
236
237 if (access_ok(dst, size)) {
238 pagefault_disable();
239 ret = __copy_to_user_inatomic(dst, src, size);
240 pagefault_enable();
241 }
242 force_uaccess_end(old_fs);
243
244 if (ret)
245 return -EFAULT;
246 return 0;
247}
248EXPORT_SYMBOL_GPL(copy_to_user_nofault);
249
250/**
251 * strncpy_from_user_nofault: - Copy a NUL terminated string from unsafe user
252 * address.
253 * @dst: Destination address, in kernel space. This buffer must be at
254 * least @count bytes long.
255 * @unsafe_addr: Unsafe user address.
256 * @count: Maximum number of bytes to copy, including the trailing NUL.
257 *
258 * Copies a NUL-terminated string from unsafe user address to kernel buffer.
259 *
260 * On success, returns the length of the string INCLUDING the trailing NUL.
261 *
262 * If access fails, returns -EFAULT (some data may have been copied
263 * and the trailing NUL added).
264 *
265 * If @count is smaller than the length of the string, copies @count-1 bytes,
266 * sets the last byte of @dst buffer to NUL and returns @count.
267 */
268long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
269 long count)
270{
271 mm_segment_t old_fs;
272 long ret;
273
274 if (unlikely(count <= 0))
275 return 0;
276
277 old_fs = force_uaccess_begin();
278 pagefault_disable();
279 ret = strncpy_from_user(dst, unsafe_addr, count);
280 pagefault_enable();
281 force_uaccess_end(old_fs);
282
283 if (ret >= count) {
284 ret = count;
285 dst[ret - 1] = '\0';
286 } else if (ret > 0) {
287 ret++;
288 }
289
290 return ret;
291}
292
293/**
294 * strnlen_user_nofault: - Get the size of a user string INCLUDING final NUL.
295 * @unsafe_addr: The string to measure.
296 * @count: Maximum count (including NUL)
297 *
298 * Get the size of a NUL-terminated string in user space without pagefault.
299 *
300 * Returns the size of the string INCLUDING the terminating NUL.
301 *
302 * If the string is too long, returns a number larger than @count. User
303 * has to check the return value against "> count".
304 * On exception (or invalid count), returns 0.
305 *
306 * Unlike strnlen_user, this can be used from IRQ handler etc. because
307 * it disables pagefaults.
308 */
309long strnlen_user_nofault(const void __user *unsafe_addr, long count)
310{
311 mm_segment_t old_fs;
312 int ret;
313
314 old_fs = force_uaccess_begin();
315 pagefault_disable();
316 ret = strnlen_user(unsafe_addr, count);
317 pagefault_enable();
318 force_uaccess_end(old_fs);
319
320 return ret;
321}
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
9bool __weak copy_from_kernel_nofault_allowed(const void *unsafe_src,
10 size_t size)
11{
12 return true;
13}
14
15#define copy_from_kernel_nofault_loop(dst, src, len, type, err_label) \
16 while (len >= sizeof(type)) { \
17 __get_kernel_nofault(dst, src, type, err_label); \
18 dst += sizeof(type); \
19 src += sizeof(type); \
20 len -= sizeof(type); \
21 }
22
23long copy_from_kernel_nofault(void *dst, const void *src, size_t size)
24{
25 unsigned long align = 0;
26
27 if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
28 align = (unsigned long)dst | (unsigned long)src;
29
30 if (!copy_from_kernel_nofault_allowed(src, size))
31 return -ERANGE;
32
33 pagefault_disable();
34 if (!(align & 7))
35 copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
36 if (!(align & 3))
37 copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
38 if (!(align & 1))
39 copy_from_kernel_nofault_loop(dst, src, size, u16, Efault);
40 copy_from_kernel_nofault_loop(dst, src, size, u8, Efault);
41 pagefault_enable();
42 return 0;
43Efault:
44 pagefault_enable();
45 return -EFAULT;
46}
47EXPORT_SYMBOL_GPL(copy_from_kernel_nofault);
48
49#define copy_to_kernel_nofault_loop(dst, src, len, type, err_label) \
50 while (len >= sizeof(type)) { \
51 __put_kernel_nofault(dst, src, type, err_label); \
52 dst += sizeof(type); \
53 src += sizeof(type); \
54 len -= sizeof(type); \
55 }
56
57long copy_to_kernel_nofault(void *dst, const void *src, size_t size)
58{
59 unsigned long align = 0;
60
61 if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
62 align = (unsigned long)dst | (unsigned long)src;
63
64 pagefault_disable();
65 if (!(align & 7))
66 copy_to_kernel_nofault_loop(dst, src, size, u64, Efault);
67 if (!(align & 3))
68 copy_to_kernel_nofault_loop(dst, src, size, u32, Efault);
69 if (!(align & 1))
70 copy_to_kernel_nofault_loop(dst, src, size, u16, Efault);
71 copy_to_kernel_nofault_loop(dst, src, size, u8, Efault);
72 pagefault_enable();
73 return 0;
74Efault:
75 pagefault_enable();
76 return -EFAULT;
77}
78
79long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
80{
81 const void *src = unsafe_addr;
82
83 if (unlikely(count <= 0))
84 return 0;
85 if (!copy_from_kernel_nofault_allowed(unsafe_addr, count))
86 return -ERANGE;
87
88 pagefault_disable();
89 do {
90 __get_kernel_nofault(dst, src, u8, Efault);
91 dst++;
92 src++;
93 } while (dst[-1] && src - unsafe_addr < count);
94 pagefault_enable();
95
96 dst[-1] = '\0';
97 return src - unsafe_addr;
98Efault:
99 pagefault_enable();
100 dst[0] = '\0';
101 return -EFAULT;
102}
103
104/**
105 * copy_from_user_nofault(): safely attempt to read from a user-space location
106 * @dst: pointer to the buffer that shall take the data
107 * @src: address to read from. This must be a user address.
108 * @size: size of the data chunk
109 *
110 * Safely read from user address @src to the buffer at @dst. If a kernel fault
111 * happens, handle that and return -EFAULT.
112 */
113long copy_from_user_nofault(void *dst, const void __user *src, size_t size)
114{
115 long ret = -EFAULT;
116 if (access_ok(src, size)) {
117 pagefault_disable();
118 ret = __copy_from_user_inatomic(dst, src, size);
119 pagefault_enable();
120 }
121
122 if (ret)
123 return -EFAULT;
124 return 0;
125}
126EXPORT_SYMBOL_GPL(copy_from_user_nofault);
127
128/**
129 * copy_to_user_nofault(): safely attempt to write to a user-space location
130 * @dst: address to write to
131 * @src: pointer to the data that shall be written
132 * @size: size of the data chunk
133 *
134 * Safely write to address @dst from the buffer at @src. If a kernel fault
135 * happens, handle that and return -EFAULT.
136 */
137long copy_to_user_nofault(void __user *dst, const void *src, size_t size)
138{
139 long ret = -EFAULT;
140
141 if (access_ok(dst, size)) {
142 pagefault_disable();
143 ret = __copy_to_user_inatomic(dst, src, size);
144 pagefault_enable();
145 }
146
147 if (ret)
148 return -EFAULT;
149 return 0;
150}
151EXPORT_SYMBOL_GPL(copy_to_user_nofault);
152
153/**
154 * strncpy_from_user_nofault: - Copy a NUL terminated string from unsafe user
155 * address.
156 * @dst: Destination address, in kernel space. This buffer must be at
157 * least @count bytes long.
158 * @unsafe_addr: Unsafe user address.
159 * @count: Maximum number of bytes to copy, including the trailing NUL.
160 *
161 * Copies a NUL-terminated string from unsafe user address to kernel buffer.
162 *
163 * On success, returns the length of the string INCLUDING the trailing NUL.
164 *
165 * If access fails, returns -EFAULT (some data may have been copied
166 * and the trailing NUL added).
167 *
168 * If @count is smaller than the length of the string, copies @count-1 bytes,
169 * sets the last byte of @dst buffer to NUL and returns @count.
170 */
171long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
172 long count)
173{
174 long ret;
175
176 if (unlikely(count <= 0))
177 return 0;
178
179 pagefault_disable();
180 ret = strncpy_from_user(dst, unsafe_addr, count);
181 pagefault_enable();
182
183 if (ret >= count) {
184 ret = count;
185 dst[ret - 1] = '\0';
186 } else if (ret > 0) {
187 ret++;
188 }
189
190 return ret;
191}
192
193/**
194 * strnlen_user_nofault: - Get the size of a user string INCLUDING final NUL.
195 * @unsafe_addr: The string to measure.
196 * @count: Maximum count (including NUL)
197 *
198 * Get the size of a NUL-terminated string in user space without pagefault.
199 *
200 * Returns the size of the string INCLUDING the terminating NUL.
201 *
202 * If the string is too long, returns a number larger than @count. User
203 * has to check the return value against "> count".
204 * On exception (or invalid count), returns 0.
205 *
206 * Unlike strnlen_user, this can be used from IRQ handler etc. because
207 * it disables pagefaults.
208 */
209long strnlen_user_nofault(const void __user *unsafe_addr, long count)
210{
211 int ret;
212
213 pagefault_disable();
214 ret = strnlen_user(unsafe_addr, count);
215 pagefault_enable();
216
217 return ret;
218}
219
220void __copy_overflow(int size, unsigned long count)
221{
222 WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count);
223}
224EXPORT_SYMBOL(__copy_overflow);