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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#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);