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1 : : /* SPDX-License-Identifier: GPL-2.0 */
2 : : #ifndef __LINUX_UACCESS_H__
3 : : #define __LINUX_UACCESS_H__
4 : :
5 : : #include <linux/sched.h>
6 : : #include <linux/thread_info.h>
7 : : #include <linux/kasan-checks.h>
8 : :
9 : : #define uaccess_kernel() segment_eq(get_fs(), KERNEL_DS)
10 : :
11 : : #include <asm/uaccess.h>
12 : :
13 : : /*
14 : : * Architectures should provide two primitives (raw_copy_{to,from}_user())
15 : : * and get rid of their private instances of copy_{to,from}_user() and
16 : : * __copy_{to,from}_user{,_inatomic}().
17 : : *
18 : : * raw_copy_{to,from}_user(to, from, size) should copy up to size bytes and
19 : : * return the amount left to copy. They should assume that access_ok() has
20 : : * already been checked (and succeeded); they should *not* zero-pad anything.
21 : : * No KASAN or object size checks either - those belong here.
22 : : *
23 : : * Both of these functions should attempt to copy size bytes starting at from
24 : : * into the area starting at to. They must not fetch or store anything
25 : : * outside of those areas. Return value must be between 0 (everything
26 : : * copied successfully) and size (nothing copied).
27 : : *
28 : : * If raw_copy_{to,from}_user(to, from, size) returns N, size - N bytes starting
29 : : * at to must become equal to the bytes fetched from the corresponding area
30 : : * starting at from. All data past to + size - N must be left unmodified.
31 : : *
32 : : * If copying succeeds, the return value must be 0. If some data cannot be
33 : : * fetched, it is permitted to copy less than had been fetched; the only
34 : : * hard requirement is that not storing anything at all (i.e. returning size)
35 : : * should happen only when nothing could be copied. In other words, you don't
36 : : * have to squeeze as much as possible - it is allowed, but not necessary.
37 : : *
38 : : * For raw_copy_from_user() to always points to kernel memory and no faults
39 : : * on store should happen. Interpretation of from is affected by set_fs().
40 : : * For raw_copy_to_user() it's the other way round.
41 : : *
42 : : * Both can be inlined - it's up to architectures whether it wants to bother
43 : : * with that. They should not be used directly; they are used to implement
44 : : * the 6 functions (copy_{to,from}_user(), __copy_{to,from}_user_inatomic())
45 : : * that are used instead. Out of those, __... ones are inlined. Plain
46 : : * copy_{to,from}_user() might or might not be inlined. If you want them
47 : : * inlined, have asm/uaccess.h define INLINE_COPY_{TO,FROM}_USER.
48 : : *
49 : : * NOTE: only copy_from_user() zero-pads the destination in case of short copy.
50 : : * Neither __copy_from_user() nor __copy_from_user_inatomic() zero anything
51 : : * at all; their callers absolutely must check the return value.
52 : : *
53 : : * Biarch ones should also provide raw_copy_in_user() - similar to the above,
54 : : * but both source and destination are __user pointers (affected by set_fs()
55 : : * as usual) and both source and destination can trigger faults.
56 : : */
57 : :
58 : : static __always_inline __must_check unsigned long
59 : : __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
60 : : {
61 : : kasan_check_write(to, n);
62 : : check_object_size(to, n, false);
63 : 3 : return raw_copy_from_user(to, from, n);
64 : : }
65 : :
66 : : static __always_inline __must_check unsigned long
67 : : __copy_from_user(void *to, const void __user *from, unsigned long n)
68 : : {
69 : : might_fault();
70 : : kasan_check_write(to, n);
71 : : check_object_size(to, n, false);
72 : 3 : return raw_copy_from_user(to, from, n);
73 : : }
74 : :
75 : : /**
76 : : * __copy_to_user_inatomic: - Copy a block of data into user space, with less checking.
77 : : * @to: Destination address, in user space.
78 : : * @from: Source address, in kernel space.
79 : : * @n: Number of bytes to copy.
80 : : *
81 : : * Context: User context only.
82 : : *
83 : : * Copy data from kernel space to user space. Caller must check
84 : : * the specified block with access_ok() before calling this function.
85 : : * The caller should also make sure he pins the user space address
86 : : * so that we don't result in page fault and sleep.
87 : : */
88 : : static __always_inline __must_check unsigned long
89 : : __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
90 : : {
91 : : kasan_check_read(from, n);
92 : : check_object_size(from, n, true);
93 : 3 : return raw_copy_to_user(to, from, n);
94 : : }
95 : :
96 : : static __always_inline __must_check unsigned long
97 : : __copy_to_user(void __user *to, const void *from, unsigned long n)
98 : : {
99 : : might_fault();
100 : : kasan_check_read(from, n);
101 : : check_object_size(from, n, true);
102 : 3 : return raw_copy_to_user(to, from, n);
103 : : }
104 : :
105 : : #ifdef INLINE_COPY_FROM_USER
106 : : static inline __must_check unsigned long
107 : 3 : _copy_from_user(void *to, const void __user *from, unsigned long n)
108 : : {
109 : : unsigned long res = n;
110 : : might_fault();
111 : 3 : if (likely(access_ok(from, n))) {
112 : : kasan_check_write(to, n);
113 : : res = raw_copy_from_user(to, from, n);
114 : : }
115 : 3 : if (unlikely(res))
116 : 3 : memset(to + (n - res), 0, res);
117 : 3 : return res;
118 : : }
119 : : #else
120 : : extern __must_check unsigned long
121 : : _copy_from_user(void *, const void __user *, unsigned long);
122 : : #endif
123 : :
124 : : #ifdef INLINE_COPY_TO_USER
125 : : static inline __must_check unsigned long
126 : 3 : _copy_to_user(void __user *to, const void *from, unsigned long n)
127 : : {
128 : : might_fault();
129 : 3 : if (access_ok(to, n)) {
130 : : kasan_check_read(from, n);
131 : : n = raw_copy_to_user(to, from, n);
132 : : }
133 : 3 : return n;
134 : : }
135 : : #else
136 : : extern __must_check unsigned long
137 : : _copy_to_user(void __user *, const void *, unsigned long);
138 : : #endif
139 : :
140 : : static __always_inline unsigned long __must_check
141 : : copy_from_user(void *to, const void __user *from, unsigned long n)
142 : : {
143 : 3 : if (likely(check_copy_size(to, n, false)))
144 : 3 : n = _copy_from_user(to, from, n);
145 : : return n;
146 : : }
147 : :
148 : : static __always_inline unsigned long __must_check
149 : : copy_to_user(void __user *to, const void *from, unsigned long n)
150 : : {
151 : 3 : if (likely(check_copy_size(from, n, true)))
152 : 3 : n = _copy_to_user(to, from, n);
153 : : return n;
154 : : }
155 : : #ifdef CONFIG_COMPAT
156 : : static __always_inline unsigned long __must_check
157 : : copy_in_user(void __user *to, const void __user *from, unsigned long n)
158 : : {
159 : : might_fault();
160 : : if (access_ok(to, n) && access_ok(from, n))
161 : : n = raw_copy_in_user(to, from, n);
162 : : return n;
163 : : }
164 : : #endif
165 : :
166 : : static __always_inline void pagefault_disabled_inc(void)
167 : : {
168 : 3 : current->pagefault_disabled++;
169 : : }
170 : :
171 : : static __always_inline void pagefault_disabled_dec(void)
172 : : {
173 : 3 : current->pagefault_disabled--;
174 : : }
175 : :
176 : : /*
177 : : * These routines enable/disable the pagefault handler. If disabled, it will
178 : : * not take any locks and go straight to the fixup table.
179 : : *
180 : : * User access methods will not sleep when called from a pagefault_disabled()
181 : : * environment.
182 : : */
183 : 3 : static inline void pagefault_disable(void)
184 : : {
185 : : pagefault_disabled_inc();
186 : : /*
187 : : * make sure to have issued the store before a pagefault
188 : : * can hit.
189 : : */
190 : 3 : barrier();
191 : 3 : }
192 : :
193 : 3 : static inline void pagefault_enable(void)
194 : : {
195 : : /*
196 : : * make sure to issue those last loads/stores before enabling
197 : : * the pagefault handler again.
198 : : */
199 : 3 : barrier();
200 : : pagefault_disabled_dec();
201 : 3 : }
202 : :
203 : : /*
204 : : * Is the pagefault handler disabled? If so, user access methods will not sleep.
205 : : */
206 : : static inline bool pagefault_disabled(void)
207 : : {
208 : 3 : return current->pagefault_disabled != 0;
209 : : }
210 : :
211 : : /*
212 : : * The pagefault handler is in general disabled by pagefault_disable() or
213 : : * when in irq context (via in_atomic()).
214 : : *
215 : : * This function should only be used by the fault handlers. Other users should
216 : : * stick to pagefault_disabled().
217 : : * Please NEVER use preempt_disable() to disable the fault handler. With
218 : : * !CONFIG_PREEMPT_COUNT, this is like a NOP. So the handler won't be disabled.
219 : : * in_atomic() will report different values based on !CONFIG_PREEMPT_COUNT.
220 : : */
221 : : #define faulthandler_disabled() (pagefault_disabled() || in_atomic())
222 : :
223 : : #ifndef ARCH_HAS_NOCACHE_UACCESS
224 : :
225 : : static inline __must_check unsigned long
226 : : __copy_from_user_inatomic_nocache(void *to, const void __user *from,
227 : : unsigned long n)
228 : : {
229 : : return __copy_from_user_inatomic(to, from, n);
230 : : }
231 : :
232 : : #endif /* ARCH_HAS_NOCACHE_UACCESS */
233 : :
234 : : extern __must_check int check_zeroed_user(const void __user *from, size_t size);
235 : :
236 : : /**
237 : : * copy_struct_from_user: copy a struct from userspace
238 : : * @dst: Destination address, in kernel space. This buffer must be @ksize
239 : : * bytes long.
240 : : * @ksize: Size of @dst struct.
241 : : * @src: Source address, in userspace.
242 : : * @usize: (Alleged) size of @src struct.
243 : : *
244 : : * Copies a struct from userspace to kernel space, in a way that guarantees
245 : : * backwards-compatibility for struct syscall arguments (as long as future
246 : : * struct extensions are made such that all new fields are *appended* to the
247 : : * old struct, and zeroed-out new fields have the same meaning as the old
248 : : * struct).
249 : : *
250 : : * @ksize is just sizeof(*dst), and @usize should've been passed by userspace.
251 : : * The recommended usage is something like the following:
252 : : *
253 : : * SYSCALL_DEFINE2(foobar, const struct foo __user *, uarg, size_t, usize)
254 : : * {
255 : : * int err;
256 : : * struct foo karg = {};
257 : : *
258 : : * if (usize > PAGE_SIZE)
259 : : * return -E2BIG;
260 : : * if (usize < FOO_SIZE_VER0)
261 : : * return -EINVAL;
262 : : *
263 : : * err = copy_struct_from_user(&karg, sizeof(karg), uarg, usize);
264 : : * if (err)
265 : : * return err;
266 : : *
267 : : * // ...
268 : : * }
269 : : *
270 : : * There are three cases to consider:
271 : : * * If @usize == @ksize, then it's copied verbatim.
272 : : * * If @usize < @ksize, then the userspace has passed an old struct to a
273 : : * newer kernel. The rest of the trailing bytes in @dst (@ksize - @usize)
274 : : * are to be zero-filled.
275 : : * * If @usize > @ksize, then the userspace has passed a new struct to an
276 : : * older kernel. The trailing bytes unknown to the kernel (@usize - @ksize)
277 : : * are checked to ensure they are zeroed, otherwise -E2BIG is returned.
278 : : *
279 : : * Returns (in all cases, some data may have been copied):
280 : : * * -E2BIG: (@usize > @ksize) and there are non-zero trailing bytes in @src.
281 : : * * -EFAULT: access to userspace failed.
282 : : */
283 : : static __always_inline __must_check int
284 : : copy_struct_from_user(void *dst, size_t ksize, const void __user *src,
285 : : size_t usize)
286 : : {
287 : 0 : size_t size = min(ksize, usize);
288 : 0 : size_t rest = max(ksize, usize) - size;
289 : :
290 : : /* Deal with trailing bytes. */
291 : 0 : if (usize < ksize) {
292 : 0 : memset(dst + size, 0, rest);
293 : 0 : } else if (usize > ksize) {
294 : 0 : int ret = check_zeroed_user(src + size, rest);
295 : 0 : if (ret <= 0)
296 : 0 : return ret ?: -E2BIG;
297 : : }
298 : : /* Copy the interoperable parts of the struct. */
299 : 0 : if (copy_from_user(dst, src, size))
300 : : return -EFAULT;
301 : : return 0;
302 : : }
303 : :
304 : : /*
305 : : * probe_kernel_read(): safely attempt to read from a location
306 : : * @dst: pointer to the buffer that shall take the data
307 : : * @src: address to read from
308 : : * @size: size of the data chunk
309 : : *
310 : : * Safely read from address @src to the buffer at @dst. If a kernel fault
311 : : * happens, handle that and return -EFAULT.
312 : : */
313 : : extern long probe_kernel_read(void *dst, const void *src, size_t size);
314 : : extern long __probe_kernel_read(void *dst, const void *src, size_t size);
315 : :
316 : : /*
317 : : * probe_user_read(): safely attempt to read from a location in user space
318 : : * @dst: pointer to the buffer that shall take the data
319 : : * @src: address to read from
320 : : * @size: size of the data chunk
321 : : *
322 : : * Safely read from address @src to the buffer at @dst. If a kernel fault
323 : : * happens, handle that and return -EFAULT.
324 : : */
325 : : extern long probe_user_read(void *dst, const void __user *src, size_t size);
326 : : extern long __probe_user_read(void *dst, const void __user *src, size_t size);
327 : :
328 : : /*
329 : : * probe_kernel_write(): safely attempt to write to a location
330 : : * @dst: address to write to
331 : : * @src: pointer to the data that shall be written
332 : : * @size: size of the data chunk
333 : : *
334 : : * Safely write to address @dst from the buffer at @src. If a kernel fault
335 : : * happens, handle that and return -EFAULT.
336 : : */
337 : : extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
338 : : extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
339 : :
340 : : /*
341 : : * probe_user_write(): safely attempt to write to a location in user space
342 : : * @dst: address to write to
343 : : * @src: pointer to the data that shall be written
344 : : * @size: size of the data chunk
345 : : *
346 : : * Safely write to address @dst from the buffer at @src. If a kernel fault
347 : : * happens, handle that and return -EFAULT.
348 : : */
349 : : extern long notrace probe_user_write(void __user *dst, const void *src, size_t size);
350 : : extern long notrace __probe_user_write(void __user *dst, const void *src, size_t size);
351 : :
352 : : extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count);
353 : : extern long strncpy_from_unsafe_user(char *dst, const void __user *unsafe_addr,
354 : : long count);
355 : : extern long strnlen_unsafe_user(const void __user *unsafe_addr, long count);
356 : :
357 : : /**
358 : : * probe_kernel_address(): safely attempt to read from a location
359 : : * @addr: address to read from
360 : : * @retval: read into this variable
361 : : *
362 : : * Returns 0 on success, or -EFAULT.
363 : : */
364 : : #define probe_kernel_address(addr, retval) \
365 : : probe_kernel_read(&retval, addr, sizeof(retval))
366 : :
367 : : #ifndef user_access_begin
368 : : #define user_access_begin(ptr,len) access_ok(ptr, len)
369 : : #define user_access_end() do { } while (0)
370 : : #define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0)
371 : : #define unsafe_get_user(x,p,e) unsafe_op_wrap(__get_user(x,p),e)
372 : : #define unsafe_put_user(x,p,e) unsafe_op_wrap(__put_user(x,p),e)
373 : : #define unsafe_copy_to_user(d,s,l,e) unsafe_op_wrap(__copy_to_user(d,s,l),e)
374 : : static inline unsigned long user_access_save(void) { return 0UL; }
375 : : static inline void user_access_restore(unsigned long flags) { }
376 : : #endif
377 : :
378 : : #ifdef CONFIG_HARDENED_USERCOPY
379 : : void usercopy_warn(const char *name, const char *detail, bool to_user,
380 : : unsigned long offset, unsigned long len);
381 : : void __noreturn usercopy_abort(const char *name, const char *detail,
382 : : bool to_user, unsigned long offset,
383 : : unsigned long len);
384 : : #endif
385 : :
386 : : #endif /* __LINUX_UACCESS_H__ */
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