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457c8996 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
c33fa9f5 IM |
2 | /* |
3 | * Access kernel memory without faulting. | |
4 | */ | |
b95f1b31 | 5 | #include <linux/export.h> |
c33fa9f5 | 6 | #include <linux/mm.h> |
7c7fcf76 | 7 | #include <linux/uaccess.h> |
c33fa9f5 | 8 | |
3d708182 MH |
9 | static __always_inline long |
10 | probe_read_common(void *dst, const void __user *src, size_t size) | |
11 | { | |
12 | long ret; | |
13 | ||
14 | pagefault_disable(); | |
15 | ret = __copy_from_user_inatomic(dst, src, size); | |
16 | pagefault_enable(); | |
17 | ||
18 | return ret ? -EFAULT : 0; | |
19 | } | |
20 | ||
1d1585ca DB |
21 | static __always_inline long |
22 | probe_write_common(void __user *dst, const void *src, size_t size) | |
23 | { | |
24 | long ret; | |
25 | ||
26 | pagefault_disable(); | |
27 | ret = __copy_to_user_inatomic(dst, src, size); | |
28 | pagefault_enable(); | |
29 | ||
30 | return ret ? -EFAULT : 0; | |
31 | } | |
32 | ||
c33fa9f5 | 33 | /** |
3d708182 | 34 | * probe_kernel_read(): safely attempt to read from a kernel-space location |
c33fa9f5 IM |
35 | * @dst: pointer to the buffer that shall take the data |
36 | * @src: address to read from | |
37 | * @size: size of the data chunk | |
38 | * | |
39 | * Safely read from address @src to the buffer at @dst. If a kernel fault | |
40 | * happens, handle that and return -EFAULT. | |
0ab32b6f AM |
41 | * |
42 | * We ensure that the copy_from_user is executed in atomic context so that | |
43 | * do_page_fault() doesn't attempt to take mmap_sem. This makes | |
44 | * probe_kernel_read() suitable for use within regions where the caller | |
45 | * already holds mmap_sem, or other locks which nest inside mmap_sem. | |
75a1a607 DB |
46 | * |
47 | * probe_kernel_read_strict() is the same as probe_kernel_read() except for | |
48 | * the case where architectures have non-overlapping user and kernel address | |
49 | * ranges: probe_kernel_read_strict() will additionally return -EFAULT for | |
50 | * probing memory on a user address range where probe_user_read() is supposed | |
51 | * to be used instead. | |
c33fa9f5 | 52 | */ |
6144a85a | 53 | |
f29c5041 | 54 | long __weak probe_kernel_read(void *dst, const void *src, size_t size) |
6144a85a JW |
55 | __attribute__((alias("__probe_kernel_read"))); |
56 | ||
75a1a607 DB |
57 | long __weak probe_kernel_read_strict(void *dst, const void *src, size_t size) |
58 | __attribute__((alias("__probe_kernel_read"))); | |
59 | ||
f29c5041 | 60 | long __probe_kernel_read(void *dst, const void *src, size_t size) |
c33fa9f5 IM |
61 | { |
62 | long ret; | |
b4b8ac52 | 63 | mm_segment_t old_fs = get_fs(); |
c33fa9f5 | 64 | |
b4b8ac52 | 65 | set_fs(KERNEL_DS); |
3d708182 | 66 | ret = probe_read_common(dst, (__force const void __user *)src, size); |
b4b8ac52 | 67 | set_fs(old_fs); |
c33fa9f5 | 68 | |
3d708182 | 69 | return ret; |
c33fa9f5 IM |
70 | } |
71 | EXPORT_SYMBOL_GPL(probe_kernel_read); | |
72 | ||
3d708182 MH |
73 | /** |
74 | * probe_user_read(): safely attempt to read from a user-space location | |
75 | * @dst: pointer to the buffer that shall take the data | |
76 | * @src: address to read from. This must be a user address. | |
77 | * @size: size of the data chunk | |
78 | * | |
79 | * Safely read from user address @src to the buffer at @dst. If a kernel fault | |
80 | * happens, handle that and return -EFAULT. | |
81 | */ | |
82 | ||
83 | long __weak probe_user_read(void *dst, const void __user *src, size_t size) | |
84 | __attribute__((alias("__probe_user_read"))); | |
85 | ||
86 | long __probe_user_read(void *dst, const void __user *src, size_t size) | |
87 | { | |
88 | long ret = -EFAULT; | |
89 | mm_segment_t old_fs = get_fs(); | |
90 | ||
91 | set_fs(USER_DS); | |
92 | if (access_ok(src, size)) | |
93 | ret = probe_read_common(dst, src, size); | |
94 | set_fs(old_fs); | |
95 | ||
96 | return ret; | |
97 | } | |
98 | EXPORT_SYMBOL_GPL(probe_user_read); | |
99 | ||
c33fa9f5 IM |
100 | /** |
101 | * probe_kernel_write(): safely attempt to write to a location | |
102 | * @dst: address to write to | |
103 | * @src: pointer to the data that shall be written | |
104 | * @size: size of the data chunk | |
105 | * | |
106 | * Safely write to address @dst from the buffer at @src. If a kernel fault | |
107 | * happens, handle that and return -EFAULT. | |
108 | */ | |
1d1585ca | 109 | |
f29c5041 | 110 | long __weak probe_kernel_write(void *dst, const void *src, size_t size) |
6144a85a JW |
111 | __attribute__((alias("__probe_kernel_write"))); |
112 | ||
f29c5041 | 113 | long __probe_kernel_write(void *dst, const void *src, size_t size) |
c33fa9f5 IM |
114 | { |
115 | long ret; | |
b4b8ac52 | 116 | mm_segment_t old_fs = get_fs(); |
c33fa9f5 | 117 | |
b4b8ac52 | 118 | set_fs(KERNEL_DS); |
1d1585ca | 119 | ret = probe_write_common((__force void __user *)dst, src, size); |
b4b8ac52 | 120 | set_fs(old_fs); |
c33fa9f5 | 121 | |
1d1585ca | 122 | return ret; |
c33fa9f5 IM |
123 | } |
124 | EXPORT_SYMBOL_GPL(probe_kernel_write); | |
dbb7ee0e | 125 | |
1d1585ca DB |
126 | /** |
127 | * probe_user_write(): safely attempt to write to a user-space 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 | */ | |
135 | ||
136 | long __weak probe_user_write(void __user *dst, const void *src, size_t size) | |
137 | __attribute__((alias("__probe_user_write"))); | |
138 | ||
139 | long __probe_user_write(void __user *dst, const void *src, size_t size) | |
140 | { | |
141 | long ret = -EFAULT; | |
142 | mm_segment_t old_fs = get_fs(); | |
143 | ||
144 | set_fs(USER_DS); | |
145 | if (access_ok(dst, size)) | |
146 | ret = probe_write_common(dst, src, size); | |
147 | set_fs(old_fs); | |
148 | ||
149 | return ret; | |
150 | } | |
151 | EXPORT_SYMBOL_GPL(probe_user_write); | |
3d708182 | 152 | |
dbb7ee0e AS |
153 | /** |
154 | * strncpy_from_unsafe: - Copy a NUL terminated string from unsafe address. | |
155 | * @dst: Destination address, in kernel space. This buffer must be at | |
156 | * least @count bytes long. | |
f144c390 | 157 | * @unsafe_addr: Unsafe address. |
dbb7ee0e AS |
158 | * @count: Maximum number of bytes to copy, including the trailing NUL. |
159 | * | |
160 | * Copies a NUL-terminated string from unsafe address to kernel buffer. | |
161 | * | |
162 | * On success, returns the length of the string INCLUDING the trailing NUL. | |
163 | * | |
164 | * If access fails, returns -EFAULT (some data may have been copied | |
165 | * and the trailing NUL added). | |
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. | |
75a1a607 DB |
169 | * |
170 | * strncpy_from_unsafe_strict() is the same as strncpy_from_unsafe() except | |
171 | * for the case where architectures have non-overlapping user and kernel address | |
172 | * ranges: strncpy_from_unsafe_strict() will additionally return -EFAULT for | |
173 | * probing memory on a user address range where strncpy_from_unsafe_user() is | |
174 | * supposed to be used instead. | |
dbb7ee0e | 175 | */ |
75a1a607 DB |
176 | |
177 | long __weak strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count) | |
178 | __attribute__((alias("__strncpy_from_unsafe"))); | |
179 | ||
180 | long __weak strncpy_from_unsafe_strict(char *dst, const void *unsafe_addr, | |
181 | long count) | |
182 | __attribute__((alias("__strncpy_from_unsafe"))); | |
183 | ||
184 | long __strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count) | |
dbb7ee0e AS |
185 | { |
186 | mm_segment_t old_fs = get_fs(); | |
187 | const void *src = unsafe_addr; | |
188 | long ret; | |
189 | ||
190 | if (unlikely(count <= 0)) | |
191 | return 0; | |
192 | ||
193 | set_fs(KERNEL_DS); | |
194 | pagefault_disable(); | |
195 | ||
196 | do { | |
bd28b145 | 197 | ret = __get_user(*dst++, (const char __user __force *)src++); |
dbb7ee0e AS |
198 | } while (dst[-1] && ret == 0 && src - unsafe_addr < count); |
199 | ||
200 | dst[-1] = '\0'; | |
201 | pagefault_enable(); | |
202 | set_fs(old_fs); | |
203 | ||
9dd861d5 | 204 | return ret ? -EFAULT : src - unsafe_addr; |
dbb7ee0e | 205 | } |
3d708182 MH |
206 | |
207 | /** | |
208 | * strncpy_from_unsafe_user: - Copy a NUL terminated string from unsafe user | |
209 | * address. | |
210 | * @dst: Destination address, in kernel space. This buffer must be at | |
211 | * least @count bytes long. | |
212 | * @unsafe_addr: Unsafe user address. | |
213 | * @count: Maximum number of bytes to copy, including the trailing NUL. | |
214 | * | |
215 | * Copies a NUL-terminated string from unsafe user address to kernel buffer. | |
216 | * | |
217 | * On success, returns the length of the string INCLUDING the trailing NUL. | |
218 | * | |
219 | * If access fails, returns -EFAULT (some data may have been copied | |
220 | * and the trailing NUL added). | |
221 | * | |
222 | * If @count is smaller than the length of the string, copies @count-1 bytes, | |
223 | * sets the last byte of @dst buffer to NUL and returns @count. | |
224 | */ | |
225 | long strncpy_from_unsafe_user(char *dst, const void __user *unsafe_addr, | |
226 | long count) | |
227 | { | |
228 | mm_segment_t old_fs = get_fs(); | |
229 | long ret; | |
230 | ||
231 | if (unlikely(count <= 0)) | |
232 | return 0; | |
233 | ||
234 | set_fs(USER_DS); | |
235 | pagefault_disable(); | |
236 | ret = strncpy_from_user(dst, unsafe_addr, count); | |
237 | pagefault_enable(); | |
238 | set_fs(old_fs); | |
239 | ||
240 | if (ret >= count) { | |
241 | ret = count; | |
242 | dst[ret - 1] = '\0'; | |
243 | } else if (ret > 0) { | |
244 | ret++; | |
245 | } | |
246 | ||
247 | return ret; | |
248 | } | |
249 | ||
250 | /** | |
251 | * strnlen_unsafe_user: - Get the size of a user string INCLUDING final NUL. | |
252 | * @unsafe_addr: The string to measure. | |
253 | * @count: Maximum count (including NUL) | |
254 | * | |
255 | * Get the size of a NUL-terminated string in user space without pagefault. | |
256 | * | |
257 | * Returns the size of the string INCLUDING the terminating NUL. | |
258 | * | |
259 | * If the string is too long, returns a number larger than @count. User | |
260 | * has to check the return value against "> count". | |
261 | * On exception (or invalid count), returns 0. | |
262 | * | |
263 | * Unlike strnlen_user, this can be used from IRQ handler etc. because | |
264 | * it disables pagefaults. | |
265 | */ | |
266 | long strnlen_unsafe_user(const void __user *unsafe_addr, long count) | |
267 | { | |
268 | mm_segment_t old_fs = get_fs(); | |
269 | int ret; | |
270 | ||
271 | set_fs(USER_DS); | |
272 | pagefault_disable(); | |
273 | ret = strnlen_user(unsafe_addr, count); | |
274 | pagefault_enable(); | |
275 | set_fs(old_fs); | |
276 | ||
277 | return ret; | |
278 | } |