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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/*
2 * Access kernel memory without faulting.
3 */
4#include <linux/export.h>
5#include <linux/mm.h>
6#include <linux/uaccess.h>
7
8/**
9 * probe_kernel_read(): safely attempt to read from a location
10 * @dst: pointer to the buffer that shall take the data
11 * @src: address to read from
12 * @size: size of the data chunk
13 *
14 * Safely read from address @src to the buffer at @dst. If a kernel fault
15 * happens, handle that and return -EFAULT.
16 *
17 * We ensure that the copy_from_user is executed in atomic context so that
18 * do_page_fault() doesn't attempt to take mmap_sem. This makes
19 * probe_kernel_read() suitable for use within regions where the caller
20 * already holds mmap_sem, or other locks which nest inside mmap_sem.
21 */
22
23long __weak probe_kernel_read(void *dst, const void *src, size_t size)
24 __attribute__((alias("__probe_kernel_read")));
25
26long __probe_kernel_read(void *dst, const void *src, size_t size)
27{
28 long ret;
29 mm_segment_t old_fs = get_fs();
30
31 set_fs(KERNEL_DS);
32 pagefault_disable();
33 ret = __copy_from_user_inatomic(dst,
34 (__force const void __user *)src, size);
35 pagefault_enable();
36 set_fs(old_fs);
37
38 return ret ? -EFAULT : 0;
39}
40EXPORT_SYMBOL_GPL(probe_kernel_read);
41
42/**
43 * probe_kernel_write(): safely attempt to write to a location
44 * @dst: address to write to
45 * @src: pointer to the data that shall be written
46 * @size: size of the data chunk
47 *
48 * Safely write to address @dst from the buffer at @src. If a kernel fault
49 * happens, handle that and return -EFAULT.
50 */
51long __weak probe_kernel_write(void *dst, const void *src, size_t size)
52 __attribute__((alias("__probe_kernel_write")));
53
54long __probe_kernel_write(void *dst, const void *src, size_t size)
55{
56 long ret;
57 mm_segment_t old_fs = get_fs();
58
59 set_fs(KERNEL_DS);
60 pagefault_disable();
61 ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
62 pagefault_enable();
63 set_fs(old_fs);
64
65 return ret ? -EFAULT : 0;
66}
67EXPORT_SYMBOL_GPL(probe_kernel_write);
68
69/**
70 * strncpy_from_unsafe: - Copy a NUL terminated string from unsafe address.
71 * @dst: Destination address, in kernel space. This buffer must be at
72 * least @count bytes long.
73 * @unsafe_addr: Unsafe address.
74 * @count: Maximum number of bytes to copy, including the trailing NUL.
75 *
76 * Copies a NUL-terminated string from unsafe address to kernel buffer.
77 *
78 * On success, returns the length of the string INCLUDING the trailing NUL.
79 *
80 * If access fails, returns -EFAULT (some data may have been copied
81 * and the trailing NUL added).
82 *
83 * If @count is smaller than the length of the string, copies @count-1 bytes,
84 * sets the last byte of @dst buffer to NUL and returns @count.
85 */
86long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count)
87{
88 mm_segment_t old_fs = get_fs();
89 const void *src = unsafe_addr;
90 long ret;
91
92 if (unlikely(count <= 0))
93 return 0;
94
95 set_fs(KERNEL_DS);
96 pagefault_disable();
97
98 do {
99 ret = __get_user(*dst++, (const char __user __force *)src++);
100 } while (dst[-1] && ret == 0 && src - unsafe_addr < count);
101
102 dst[-1] = '\0';
103 pagefault_enable();
104 set_fs(old_fs);
105
106 return ret ? -EFAULT : src - unsafe_addr;
107}